Abstract:
The present invention provides a method for controlling vehicle airbag status during a vehicle dynamic situation. The method initially includes estimating an occupant classification. This estimation may, for example, be based on the occupant&#39;s weight. Thereafter, a plurality of indicators which may signify an impending vehicle dynamic situation are evaluated. If any of the indicators signify an impending vehicle dynamic situation, the occupant classification is held constant. Therefore, the events of the vehicle dynamic situation are prevented from contributing to an incorrect occupant classification.

Description:
TECHNICAL FIELD 
     The present invention pertains generally to a method for controlling airbag status during a vehicle dynamic situation. 
     BACKGROUND OF THE INVENTION 
     It is well known to establish a vehicle occupant classification such as, for example, by measuring the weight of an occupant. Vehicle occupant classification information identifies the type of occupant seated within a vehicle and generally includes the following three categories: adult, child, or none. This information may be useful, for example, in determining whether or not to deploy an airbag. As an example, it may be desirable to deploy an airbag under certain circumstances if the vehicle occupant in a particular seat is an adult, but the airbag may not be deployed if the vehicle occupant is a child or if the particular seat is empty. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method for controlling airbag status during a vehicle dynamic situation. The method initially includes estimating an occupant classification. This estimation may, for example, be based on the occupant&#39;s weight. Thereafter, a plurality of indicators which may signify an impending vehicle dynamic situation are evaluated. If any of the indicators signify an impending vehicle dynamic situation, the occupant classification is held constant. Therefore, the events of the vehicle dynamic situation are prevented from contributing to an inappropriate change of occupant classification. 
     The step of evaluating a plurality of indicators may include checking an antilock brake system status. 
     The step of evaluating a plurality of indicators may include checking the vehicle&#39;s speed. 
     The step of evaluating a plurality of indicators may include checking the degree of brake system application. 
     The step of evaluating a plurality of indicators may include checking a stability control system status. 
     An alternate method of the present invention is also adapted to control airbag status. The alternate method initially includes estimating an occupant classification, and thereafter selecting an air bag status based on the estimated occupant classification. A plurality of indicators which may signify an impending vehicle dynamic situation are then evaluated. If any of the indicators signify an impending vehicle dynamic situation, the air bag status is held constant. Therefore, the events of the vehicle dynamic situation are prevented from contributing to an inappropriate air bag status change. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart illustrating a method in accordance with the preferred embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like components,  FIG. 1  shows method  10  (also referred to herein as algorithm  10 ) in accordance with the present invention. More precisely,  FIG. 1  shows a block diagram representing steps performed by a control module (not shown). 
     At step  12 , the algorithm  10  checks the status of the vehicle&#39;s antilock brake system. At step  14 , if the vehicle&#39;s antilock brake system is not activated, the algorithm  10  returns to step  12  and continues checking for antilock brake activation. At step  14 , if the vehicle&#39;s antilock brake system is activated, a positive (i.e., “yes” or “true”) indication is transmitted to the logic gate at step  34  which will be described in detail hereinafter. 
     At step  16 , the algorithm  10  checks the vehicle&#39;s current speed. At step  18 , the algorithm  10  determines whether the vehicle&#39;s current speed exceeds a predefined speed threshold (e.g., 45 mph). If at step  18  the vehicle&#39;s current speed does not exceed the predefined speed threshold, the algorithm  10  returns to step  16  and continues checking the current vehicle speed. If at step  18  the vehicle&#39;s current speed does exceed the predefined speed threshold, a positive indication is transmitted to the logic gate at step  24  which will be described in detail hereinafter. 
     At step  20 , the algorithm  10  checks the degree to which the vehicle&#39;s brake system is applied. The degree of brake system application may, for example, be estimated by monitoring the brake pedal position. Alternatively, the degree of brake system application may be estimated by monitoring the pressure in the brake system with a conventional pressure sensor. At step  22 , the algorithm  10  determines whether the degree to which the vehicle&#39;s brake system is applied exceeds a predefined braking threshold (e.g., 40% applied). If at step  22  the degree of brake system application does not exceed the predefined braking threshold, the algorithm  10  returns to step  20  and continues checking the brake system. If at step  22  the degree of brake system application does exceed the predefined braking threshold, a positive indication is transmitted to the logic gate at step  24 . 
     While the predefined speed and braking thresholds of steps  18  and  22  have been described as being independent, they may be correlated with each other. In other words, the predefined speed threshold may decrease as the predefined braking threshold increases and vice versa. For example, if the vehicle is traveling relatively slowly (e.g., 15 mph), the conditions of steps  18  and  22  can both be met only if a relatively large amount of braking is applied (e.g., 60% application). Conversely, if the vehicle is traveling relatively quickly (e.g., 65 mph), the conditions of steps  18  and  22  can both be met if only a relatively small amount of braking is applied (e.g., 30% application). 
     The logic gate of step  24  is an “and gate” meaning that a positive indication is transmitted to the logic gate at step  34  only if both inputs into the logic gate  24  are positive. If either or both of the inputs into the logic gate  24  are negative, the algorithm  10  transmits a negative indication to the logic gate  34 . 
     At step  26 , the algorithm  10  checks the status of the vehicle&#39;s stability control system. As is known in the art, a “stability control system” is a vehicle system configured to retain control of a vehicle during certain dynamic events. For example, if the vehicle is skidding, the stability control system may reduce engine output and/or apply the brake system in a manner adapted to regain traction. At step  28 , if the vehicle&#39;s stability control system is not activated, the algorithm  10  returns to step  26  and continues checking for stability control system activation. At step  28 , if the vehicle&#39;s stability control system is activated, a positive indication is transmitted to the logic gate at step  34 . 
     At step  30 , the algorithm  10  checks any other vehicle conditions which may be indicative of a significant vehicle dynamic situation such as a collision. The specific indicative conditions may differ depending on the type of vehicle. As an example, a vehicle having an automatic crash preparation system may provide information indicative of a significant vehicle dynamic situation. As a further example, a radar system configured to measure the proximity of foreign objects may also provide information indicative of a significant vehicle dynamic situation. At step  32 , if no conditions indicative of a significant vehicle dynamic situation have been identified, the algorithm  10  returns to step  30 . At step  32 , if any condition indicative of a significant vehicle dynamic situation has been identified, a positive indication is transmitted to the logic gate at step  34 . 
     The logic gate of step  34  is an “or gate” meaning that if at least one of the inputs thereto are positive, the algorithm  10  proceeds to step  36 . If none of the inputs to the logic gate of step  34  are “yes”, the occupant classification status is not adjusted by the method of the present invention and is therefore calculated in a conventional manner. 
     The inputs into the logic gate of step  34  are indicators intended to signify an impending significant vehicle dynamic situation such as a collision. It should, however, be appreciated that the present invention does not require all of the indicators shown in  FIG. 1 . As an example, a vehicle without antilock brakes can implement the method of the present invention by focusing on the remaining indicators to anticipate a significant vehicle dynamic situation. 
     At step  36 , the algorithm  10  holds constant the current occupant classification. Vehicle occupant classification information identifies the type of occupant seated within a vehicle and generally includes the following three categories: adult, child, or none. This information may be useful, for example, in determining whether or not to deploy an airbag. As an example, it may be desirable to deploy an airbag under certain circumstances if the vehicle occupant in a particular seat is an adult, but the airbag may not be deployed if the vehicle occupant is a child or if the particular seat is empty. 
     Occupant classification estimation is well known and is generally based on relevant quantifiable data such as, for example, the occupant&#39;s weight. Such data may change to reflect the events of a significant vehicle dynamic situation and thereby yield a false indication of the occupant&#39;s classification. As an example, a relatively large measured weight indicative of an adult occupant may be reduced thereby indicating a child classification during heavy vehicle braking which moves the occupant toward the edge of the seat. 
     In response to one or more indications of an impending significant vehicle dynamic situation, step  36  assumes that the occupant classification (i.e., adult, child or empty) should not change during a subsequent dynamic situation and therefore holds the current occupant classification constant as long as the output of the logic gate of step  34  is positive, up to a pre-defined period of time. Accordingly, by preventing the occupant classification from changing during a subsequent dynamic situation, step  36  eliminates the potential for a false indication of the occupant&#39;s classification based data which changes to reflect the events of the vehicle dynamic situation. 
     According to an alternate embodiment of the present invention, step  36  may be replaced by step  36   a  such that the air bag status is held constant rather than the occupant classification. Step  36   a  assumes that the air bag status (i.e., activated or deactivated) should not change during a subsequent dynamic situation and therefore holds the current air bag status constant. Accordingly, by preventing the air bag status from changing during a subsequent dynamic situation, step  36   a  eliminates the potential for an inappropriate air bag status caused by a false indication of the occupant&#39;s classification which changes to reflect the events of the vehicle dynamic situation. It should be appreciated that steps  36  and  36   a  perform substantially the same function in a slightly different manner and are therefore interchangeable. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.