Abstract:
A method and system for estimating the amount of forward displacement undergone by a seat-belted occupant of a vehicle. A test dummy, representing the seat-belted occupant, is pivotably restrained at a first point with respect to a fixed frame of reference. A second point associated with the test dummy is subsequently subjected to a measurable amount of forward displacement with respect to the same frame of reference, causing the test dummy to lean or tilt forward. An amount of forward displacement that occurs at a third point on or adjacent to the test dummy is then estimated through the use of ratios.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to the field of vehicle safety systems. More specifically, the present invention relates to a system for simulating the movement of a seat-belted occupant of a vehicle, along with a method of estimating the amount of horizontal displacement undergone by the seat-belted occupant.  
       BACKGROUND OF THE INVENTION  
       [0002]     Vehicle manufactures frequently utilize various systems and methods to simulate an occupant of a vehicle during sudden deceleration. These simulations typically allow the vehicle manufactures to predict the types of movement that the body of a vehicle occupant will undergo during a moment of sudden vehicle deceleration. The simulation results are then used to evaluate and improve various safety features found in modern vehicles. One such recent feature has been smart air bag systems, which monitor the actual position and motion of an occupant&#39;s body to determine an appropriate course of action.  
         [0003]     In order to develop and test systems such as smart airbags, manufacturers need to be able to simulate and map the position and motion of a vehicle occupant during various conditions. However, existing methods of simulating the motion of a vehicle occupant are unable to provide a quick and simple way of accurately simulating the movement of a seat-belted occupant during a moment of vehicle deceleration and then estimate the resulting displacement of the seat-belted occupant from his original position. Accordingly, the inventor of the present invention has developed a system and method for easily simulating the movement of a seat-belted occupant and estimating the amount of forward displacement that the occupant would be subject to due to sudden deceleration of the vehicle.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention relates to the field of vehicle safety, and more specifically, to a system and method of simulating the movement of a seat-belted occupant of a vehicle by subjecting a first, fixed point associated with a test dummy to a measurable amount of forward displacement with respect to a fixed frame of reference while limiting the amount of forward displacement that can occur at a second fixed point associated with the dummy with respect to the same frame of reference. Through the use of ratios, an amount of overall forward displacement undergone by the test dummy can then be estimated. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a simplified illustration of a system for simulating a seat-belted occupant according to one embodiment of the present invention.  
         [0006]      FIG. 2  is a simplified illustration of how the system of  FIG. 1  operates.  
         [0007]      FIG. 3  illustrates the various distances and displacements used to determine the amount of horizontal or forward displacement that a seat-belted occupant may experience during deceleration of their vehicle. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0008]     A preferred embodiment of the present invention will now be described with reference to  FIGS. 1 through 3 . In general, a seat-belted occupant simulator  50  comprises two sections, including a mount  100  and an attached test dummy  200 . Mount  100  includes a support guide  110  that establishes a fixed frame of reference with respect to the test dummy  200 . Support guide  110  can be selectively fixed to a stationary structure, such as a wall or floor. Alternatively, mount  100  can be selectively fixed to an appropriate mobile structure, thereby allowing the simulator  50  to be easily moved from one location to another.  
         [0009]     Located on support guide  110  is a drive guide  120  that is capable of being linearly displaced back and forth along the support guide  110 . Movement of drive guide  120  relative to support guide  110  can be accomplished in numerous ways, ranging from something as simple as a human operator manually displacing drive guide  120  relative to support guide  110 , to something more complex, such as a computer-controlled motor capable of accurately displacing drive guide  120  for various predetermined distances at one or more selectable velocities (not shown). To measure how much drive guide  120  is extended or displaced relative to support guide  110  at any moment in time, a displacement monitor  150  is incorporated into the mount system  100 .  
         [0010]     According to the present embodiment, a support brace  130  is affixed to the test dummy  200 . Drive guide  120  then supports test dummy  200  by connecting to the support brace  130 . As illustrated in the Figures, drive guide  120  connects to support brace  130  at point B. This connection at point B between drive guide  120  and support brace  130  functions as a pivot point, allowing the support brace  130 , and subsequently the test dummy  200  affixed to support brace  130 , to pivot or rotate about point B.  
         [0011]     In order to simulate the tilting or leaning motion of a seat-belted occupant, one end of test dummy  200  must generally be fixed with respect to the fixed frame of reference represented in the current embodiment by the support guide  110 . This is accomplished by various restraining systems  140  that, in general, prevent the fixed end of the test dummy  200  from undergoing any forward-directed lateral displacement. According to a first embodiment, not illustrated, restraining system  140  can comprise some form of mechanical or electromechanical brake or catch that secures point A of the mounting brace  130  from undergoing any forwardly-directed displacement relative to the support guide  110 . For example, restraining system  140  can comprise a rigid bar or member that is fixed in length, and thus cannot be shortened through compaction or lengthened through extension. One end of the rigid member attaches to a point on the fixed frame of reference, such as one end of the support guide  110 . The other end of the rigid member attaches either to the test dummy  200  or to the mounting brace  130  in such a manner that the test dummy  200  is restricted from any linear displacement in either a forwards or backwards direction with respect to the established fixed frame of reference. At the same time, however, the rigid member connects to the support brace  130  or test dummy  200  in such a manner as to allow the support brace  130  and/or test dummy  200  to rotate or pivot about the connection point.  
         [0012]     According to an alternate embodiment, as illustrated in the Figures, the restraining system comprises a flexible tether  140  that connects in-between support guide  110  and point A on the support brace  130 . As in the prior embodiment discussed above, the connection at point A functions as a pivot point, permitting the support brace  130  and/or test dummy  200  to pivot or rotate about point A. However, unlike the prior embodiment, the flexible tether  140  prevents point A of the support brace  130  from undergoing any forward-directed displacement, relative to the support guide  110 , only after the drive guide  120  has been extended by an amount that equals the length of the flexible tether  140 . Accordingly, in this embodiment of the invention, simulations should only be considered active once the tether  140  is fully extended, thus assuring that point A of the support brace  130  cannot undergo any further forward-directed displacement.  
         [0013]     To assure that measurements are taken only after tether  140  has been fully extended, an angle sensor or inclinometer (not shown) can be incorporated into the simulator system  50  at point B. Upon drive guide  120  extending far enough to equal the length of tether  140 , the test dummy  200  will begin to tilt forward. The inclinometer mounted at point B will detect the tilting motion of test dummy  200  and can be setup to mark that point in time and space as the starting or reference point for all subsequent measurements or estimates obtained through use of the simulator system  50 .  
         [0014]     Operation of the seat-belted occupant simulator  50  will now be described with reference to the Figures. According to a first example, it is presumed that test dummy  200  is initially placed in a vertical orientation so that the length of test dummy  200  lies perpendicular to the length of the support guide  110 . This vertical orientation, as illustrated in  FIG. 1 , best represents a vehicle occupant sitting upright in their seat. The motion that a vehicle occupant subsequently undergoes upon sudden deceleration of their vehicle is simulated by displacing drive guide  120  in a forward direction. This results in an upper portion of the test dummy  200  being displaced forward relative to the fixed frame of reference while the lower portion of the test dummy  200  is held in place due to the restraint system  140 . Consequently, the test dummy  200  undergoes a tilting motion similar to that of a seat-belted occupant, leaning both forward and downward.  
         [0015]     For purposes of evaluating safety systems such as seat belts and air bags, it is advantageous for a vehicle manufacturer to be able to estimate the amount of forward displacement undergone by an occupant&#39;s body at any point during a sudden deceleration situation. The seat-belted occupant simulator  50  is advantageous in this respect as it subsequently allows for an easy and rapid estimation of the amount of forward displacement undergone by the test dummy  200  by means of a simple ratio comparison.  
         [0016]     When a vehicle occupant is caught in a state of sudden deceleration and their body is leaning or tilting forward, the outermost part of their body that faces in a forward direction will be the first portion of their body to likely impact the dashboard  300  or trigger an air-bag system. In the embodiment illustrated in the Figures, this outermost part of an occupant is presumed to be the nose, illustrated as point F on the test dummy  200 , although any point on the test dummy  200  could be utilized.  
         [0017]     To estimate the amount of forward displacement undergone by the outermost region (point F) of the test dummy  200 , one must first determine the distance that drive guide  120  has been displaced in the forward direction relative to the support guide  110 . If the restraint system  140  that is being utilized is based on a flexible tether, then this determined amount of displacement must be evaluated in relation to the amount of forward displacement inherently allowed by the flexible tether. The overall amount of forward displacement undergone by drive guide  120  must then be reduced by the amount of displacement allowed by the tether, which is equivalent to the tether length. In the illustrated embodiment, the adjusted distance is graphically depicted in  FIG. 3  as the line connecting the two points labeled B and C, respectively. This distance BC can then be related to the distance or amount of forward displacement undergone by the upper portion of the test dummy  200 , indicated in  FIG. 3  as the line connecting the two labeled points D and E. Specifically, the ratio DE/BC is assumed to be equal to the ratio of the distances AD/AB, where AD is the distance between point A on said mounting brace  130 , and point D, representing the vertical height of the selected outermost point F of the test dummy  200 . Similarly, distance AB represents the vertical distance that exists between points A and B on said mounting brace  130 . As points A, B and D are all known, distances AB and AD, which are at right angles to distances BC and DE, can be readily determined. Knowing distances BC, AB and AD, unknown distance DE can then be readily estimated through the relationship: 
 
 DE=BC* ( AD/AB )
 
 Resultant distance DE represents the relative amount of horizontal or forward displacement undergone by the upper portion of test dummy  200 . However, it does not take into account the position of the outermost part of the test dummy  200 , represented by point F. Accordingly, an offset representing the distance between point D and point F must be added to the calculated distance DE. The resultant amount of forward displacement undergone by test dummy  200  is then seen to be: 
 
Displacement= BC* ( AD/AB )+ DF 
 
 In the above equation, the estimated offset distance DF is readily predetermined through measurement. 
 
         [0020]     In addition to the distance or amount of forward displacement undergone by the test dummy, once can also readily estimate the velocity that the test dummy was subject to during its displacement. This is accomplished by simply recording the amount of time required to displace the test dummy from its initial starting position to its final displaced state, and then dividing the test dummy&#39;s estimated amount of forward displacement by this recorded amount of time.  
         [0021]     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.