Abstract:
A crash sensing system for determining a vehicle impact includes an electronic controller for activating impact mitigation equipment during both a first stage event and a second stage event. One or more sensors are used for determining the magnitude of both frontal and side impact forces during the vehicle impact. The controller operates to adjust the sensitivity of the sensors based upon vehicle speed measurements.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/926,341 filed on Apr. 26, 2007, and assigned to Delphi Technologies, Inc. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to deployable vehicle restraining systems and more particularly to a sensing system enhancement for use with dual stage airbags. 
       BACKGROUND OF THE INVENTION 
       [0003]    Deployable restraints have been used for many years to mitigate occupant injuries in vehicle crashes. These restraints operate by detecting a collision and inflating one or more air bags that act to prevent the driver and/or passenger from contacting the steering wheel or dashboard. Because of the time required to deploy most restraints, the sensor system must be able to predict the deployment of the restraint well in advance of the time it is actually used by the occupant. Generally, the sooner the sensor system recognizes a collision and deploys the restraint, the lesser the chance of driver and/or passenger injury. 
         [0004]    As seen in prior art  FIG. 1 , a typical restraint system uses computer and algorithm to operate the restraint system  100  that consists of a sensing and diagnostic module (SDM)  101  as well as one or more electronic frontal sensor(s) (EFS)  103 , side impact sensors (SIS)  102 , and appropriate deployable restraints  104 . The SDM  101  is typically located in the passenger compartment and contains a computer/microprocessor to execute a sensing algorithm along with two accelerometers  105  and  107 . The accelerometers  105 ,  107  are oriented in a manner to measure vehicle longitudinal and lateral decelerations for providing both safety and backup deployment functions. The EFS  103  is located in the forward portion of the vehicle for providing early impact detection in frontal collisions. The SIS  102  is located in the door or side structure of the vehicle to provide early impact detection in side collisions. The SIS  102  and EFS  103  also include an accelerometer and appropriate signal conditioning and communication circuitry (which may include a microprocessor) for transmitting changes in vehicle velocity to the SDM  101 . 
         [0005]    As known in the art, the algorithm located in the SDM typically measures the change in velocity that occurs as the EFS sensor is decelerated by an impact where forces are applied to the device as a result of the crushing vehicle structure. This accumulated change in velocity represents an estimate of the vehicle&#39;s initial contact velocity (V 0 ). The V 0  estimate from the EFS location occurs much earlier in the crash than the measured final velocity from the SDM in the passenger compartment. Thus, the location of the EFS will affect how quickly a peak velocity is measured. As the mounting location moves rearward from the front of the vehicle, the cumulative time required to make an accurate peak velocity measurement increases. 
         [0006]    Also as known in the art, accelerometers are used to estimate V 0  because they have the added advantage of taking into consideration the mass of the impacted object. The severity of a collision with respect to an occupant is proportional to both the speed at impact (V 0 ) and the mass of the impacted object. Striking a heavy object (such as another vehicle) at a given speed may produce a large vehicle deceleration with consequent risk of injury to vehicle occupants, but striking a light object (such as a traffic barrel) at the same speed would produce an insignificant deceleration with little or no risk to the occupants. Hence, the use of vehicle speed alone is generally insufficient to determine if the impact will produce significant occupant injuries requiring restraint. 
         [0007]    It is further known in the art that inflatable restraints may be provided with the capability for multiple levels of restraint force. These multiple levels, or stages, are provided to adapt the restraint to different conditions of accident severity, occupant size, occupant position, restraint configuration, etc. For example, a first stage deployment may only require the vehicle&#39;s airbag to be partially filled with gas if the impact is below some threshold V 0  value, while a second stage deployment may require the airbag to be completely filled at some higher threshold value. Hence, it is important for a sensing system to be able to determine whether an event requires a first stage or a second stage airbag deployment. Whether a first stage or second stage deployment is triggered is typically based on the type of forces involved in a vehicle crash. This will depend on the particular type and speed of the vehicle crash. For example, an offset deformable barrier (ODB) impact may require a lower V 0  threshold for second stage airbag deployment than a rigid frontal barrier impact. This additional dimension of dual stage airbags can make sensing calibrations difficult. Calibrating a sensing algorithm to properly deploy dual stage airbags for offset deformable barrier (ODB) and angle crashes can result in tradeoffs with the dual stage calibrations for full frontal threshold-airbag-desired crashes. Adjusting second stage thresholds for timely deployments for ODB and angle-type crashes can often lead to a calibration that is too sensitive for full frontal impacts, where the result is an unwanted second stage deployments for lower vehicle speed full frontal crashes. This invention provides a novel method of addressing these issues. 
       SUMMARY OF THE INVENTION 
       [0008]    A crash sensing system for determining a vehicle impact includes an electronic controller for activating impact mitigation equipment during both a first stage event and second stage event. The first stage event partially inflates an air bag and/or activates a seatbelt pretensioner and a second stage event fully inflates an air bag. One or more sensors are used for determining the magnitude of both frontal and side impact forces during the vehicle impact. The controller operates to adjust the sensitivity of the sensors based upon vehicle speed measurements. The electronic controller activates equipment to mitigate injuries in frontal impact and side impact collisions. 
         [0009]    These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0011]      FIG. 1  is a prior art block diagram of a sensing and diagnostic module (SDM) used in connection with an electronic frontal sensor (EFS) and side impact sensors (SIS) to control a typical deployable restraint system; 
           [0012]      FIG. 2  is block diagram illustrating an SDM as used in accordance with an embodiment of the invention; 
           [0013]      FIG. 3  is a flowchart diagram illustrating the steps of a method for use in an improved vehicular collisions sensing system in accordance with an embodiment of the invention; and 
           [0014]      FIG. 4  is a logic diagram describing a method of implementation of the invention. 
       
    
    
       [0015]    Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to an improved vehicular collision sensing system. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. 
         [0017]    In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
         [0018]    The present invention is an enhancement to the “acceleration based” algorithms and systems used in the prior art to improve vehicular collision sensing systems. As shown in  FIG. 2 , the invention uses vehicle speed measurements  202  typically available via the vehicle communication local area network (LAN) and/or any other direct digital or analog data source to adjust the sensitivity of the sensing system. This embodiment includes a typical SDM  201  with accelerometers for sensing frontal and side impact collisions and a computer to process acceleration and speed data and activate restraint deployment. The computer within the SDM  201  contains an algorithm to control the functions of the overall system  200 , a portion of which algorithm is described in the flowchart  FIG. 3  and the logic diagram  FIG. 4  and which comprises the essence of the invention. The embodiment also includes satellite sensors  203  and  204  located at the periphery of the vehicle with accelerometers for early crash detection, and one or more restraint systems  205  and  206  to mitigate occupant injuries in crashes. These restraints may provide a single level or stage of restraint or may be capable of providing multiple levels or stages of restraint. The invention is intended to improve the management of these multiple stages by improving the method of progressing from the lowest level of restraint (stage  1 ) to the highest level of restraint (stage  2  . . . n.) The favored embodiment may also include multiple or alternative sensors to assist or replace the accelerometers in determining if an impact has occurred with an object of sufficiently large mass to render a significant risk of injury to the vehicle occupants. These sensors may include a mechanical sensor  207 , such as an arming or safeing sensor which uses vehicle deceleration to move a mass and cause closure of an electrical contact, an impact pressure sensor  208 , which uses the pressure caused by the collapse of an interior space to signify impact severity, a piezo-electric or piezo-resistive sensor  209 , which measures the deflection of a component of the vehicle such as the bumper to assess impact severity, or a vision based sensor  210 , which uses imaging techniques to estimate the mass of an impacting object. 
         [0019]    It should be noted that the essence of the invention is based on the proposition that if the accelerometer based crash-sensing system has discriminated a first stage event, it can be assumed that an object of significant mass has been impacted. Vehicle speed can then be used to immediately determine if additional stages should be deployed. This can eliminate the need to wait for deceleration alone to build to a higher V 0  threshold level appropriate for a second stage deployment. Thus the time required to determine if a second stage deployment is required can be significantly reduced. 
         [0020]      FIG. 3  illustrates a flow chart diagram showing the improved vehicular collision sensing system in accordance with an embodiments of the invention. As shown in  FIG. 3 , a typical sensing algorithm  300  includes the calculation of various severity measures  301  such as filtered accelerations, accumulated velocity, estimated displacement, etc. The algorithm may also include a pretensioner deployment control  302  that uses the calculated severity measures compared to low-level calibration thresholds to deploy seatbelt pretensioners  303 . The algorithm will also include comparison of the severity measures with higher-level thresholds  304  to determine the need for a first stage airbag deployment  305 . In accordance with the present invention, if the accelerometer based crash sensing system has discriminated a first stage event  305  and if the vehicle speed is greater than a calibratable speed threshold  306 , then a second stage airbag is deployed  307 . To ensure that a second stage airbag deployment occurs in severe crashes where vehicle speed is low and the speed of impact is caused by motion of the impacted object, a solely acceleration based discrimination  308  is provided to deploy the second stage  309 . The acceleration based severity measures can originate from an SDM, an EFS or a relationship of these two measures. 
         [0021]    Thus, an embodiment of the invention allows calibration of the second stage severity thresholds for frontal crashes arbitrarily above a typical 16 miles per hour (MPH) first stage severity threshold allowing a lower and more sensitive second stage severity threshold for ODB and angle crashes when vehicle speeds are greater than a typical 18 MPH at the time the algorithm is enabled. Thus, the invention allows faster deployment of second stage airbags for all frontal crashes as well as providing greater flexibility in selecting second stage thresholds for ODB, angle, and other non-rigid barrier impacts. 
         [0022]    As shown in  FIG. 4 , the invention can be implemented by adding logic to an existing sensing algorithm. The new logic provides a logical “AND” function to the first stage discrimination status with a vehicle speed greater than a speed-threshold status and with a second stage severity measure greater than an acceleration-based severity-measure-threshold status to estimate the crash severity and set the second stage airbag discrimination status as appropriate. Thus, the improved method of vehicular collision detection system  400  includes a determination if the first stage discrimination has occurred  401 . The vehicle speed just prior to the algorithm enable is compared to a vehicle speed threshold  403  which typically is greater than 18 mph. This signal is combined with the first stage discrimination signal and a vehicle acceleration based measure  407 , which is greater than a threshold  405  chosen to compliment the speed-based threshold. The acceleration based measure  307  may be provided by either the SDM or the EFS or both, and may be derived from acceleration, velocity or displacement. If all of these values are present as true at the logical AND  409 , then a second stage determination is discriminated  411 . The result of the second stage discrimination is presented to a logical OR  415  such that either the final second stage discrimination  417  may occur based upon the existing second stage algorithm  413  or by a determination made through the result  411  reached through the logical AND process  409 . 
         [0023]    It will be understood by those who practice the invention and those skilled in the art, that various modifications and improvements may be made to the invention without departing from the spirit of the disclosed concept. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.