Abstract:
The invention is an apparatus for simulating attributes of a vehicle during a certain inertial event. The apparatus comprises a rigid shell, an occupant compartment surrounded by the rigid shell, and a carriage supporting the occupant compartment and the rigid shell. The test apparatus transforms the vehicle into a system of reusable components. The rigid body shell eliminates damage to body components by protecting the occupant compartment. The invention also provides a method of simulating a tripped rollover event of a vehicle with the test apparatus and a cart.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to an apparatus and a method for simulating vehicle rollover crash testing and more particularly, to an apparatus and a method which are adapted to provide repeatable, non-destructive and reliable rollover simulations.  
       BACKGROUND OF THE INVENTION  
       [0002]     Rollover crash tests are commonly used in the development of rollover detection sensors, algorithms and occupant protection systems. As in many other crash tests, partial damage or complete destruction of the vehicle is not uncommon. The building of new vehicle prototypes alone is a costly endeavor which requires engineers to attempt to maximize the amount of data and analysis gained from a limited number of crash tests available.  
         [0003]     Due to the limited availability of destructive crash tests, a majority of the tests used to develop current rollover detection algorithms and occupant protection systems are laboratory based. Safety engineers and researchers have sought to develop component level testing methods that replicate key aspects of a crash test in a repeatable and non-destructive manner. Laboratory based rollover tests often utilize a mechanism, such as sliding a vehicle into a curb or placing the vehicle on a cart and decelerating the cart, to induce vehicle roll. For tripped rollover tests, the key phase events of which the occupant compartment is involved are: the vehicle lateral velocity phase, the tripping or transition to rotation phase, the free flight rotation phase, and the ground impact or landing phase.  
         [0004]     Conventional testing attempts to simulate or replicate a few of the key phases of a given crash test. “Spit Test” type devices are capable of generating the free flight motion often seen in the airborne phase of a rollover test. The Dynamic Rollover Fixture and the Rollover Restraint Tester were developed by NHTSA and are examples of these types of devices. “Spit Test” type devices that are capable of generating the free flight motion often seen in the airborne phase of a rollover. The driving force for these devices is provided by a drop tower and free-weight system. The angular velocity ranges from 180°/s to 290°/s and is generated by various combinations of drop weight and drop height. However, it focuses only on the rotational motion occurring during the free flight phase of a typical rollover crash test.  
         [0005]     Another conventional testing device which does not include all of the key phases was developed by Breed. This device includes only a portion of the occupant compartment and simulates a quarter turn roll with no free flight motion. The fixture is accelerated using a HYGE™ sled to reach the desired lateral velocity, and the “compartment” is pushed outward by hydraulic pistons at the bottom, causing the compartment fixture to rotation clockwise about the pivot at the top of the compartment fixture allowing the dummy to experience a vehicle rotation. However, this device fails to simulate the occupant compartment free flight or landing phases.  
         [0006]     Another conventional testing device attributed to Pywell et al. simulates different quasi-static vehicle rollover conditions for characterizing various belt restraint systems in terms of dummy&#39;s excursion. This device can generally achieve a peak roll rate from 240°/s to 360°/s with a rotation up to 180°. However, it fails to simulate the occupant compartment flight phase or the landing phase.  
         [0007]     To date, most of the methods used in rollover tests and reported in the literature are either dynamic or quasi-static tests that involve rotating or “inverting” an occupant around a stationary axis. Many have been successful in simulating the rotational phase of a rollover test. However, they fail to take a vehicle&#39;s lateral translational motion into consideration. These methods primarily have been used for occupant motion studies, restraint system evaluation and development. Since most vehicle laboratory based rollover events utilize a tripping mechanism that generates lateral vehicle motion, the aforementioned methods fail to adequately characterize the transition of the occupant compartment from lateral to rotational vehicle motion. Additionally, the effects of ground contact are either not simulated or done in a very simplistically manner.  
         [0008]     Therefore, a new component rollover test device and methodology is needed. A repeatable, reusable and representative component level testing which incorporates all of the key phases could potentially be instrumental in developing robust occupant restraint systems, rollover detection sensors and understanding occupant kinematics during rollovers.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention of a component rollover test apparatus resolves the problems of the prior art. The invention is an apparatus for simulating attributes of a vehicle during a certain inertial event. The apparatus comprises a rigid shell, an occupant compartment surrounded by the rigid shell, and a carriage supporting the occupant compartment and the rigid shell.  
         [0010]     One advantage of the test apparatus is it provides the potential to develop rollover restraint and sensor systems in a more timely and economically efficient manner. The test apparatus transforms a crash test of a vehicle into a system of reusable components. The rigid body shell eliminates damage to body components by protecting representing the occupant compartment. The rigid body also provides the ability to adjust and specify center transition of gravity, inertial properties, and ride height. lateral vehicle motion into rotational motion commonly seen in laterally tripped laboratory rollover crash tests. The test apparatus also provides the potential to develop rollover restraint and sensor systems in a more timely and economically efficient manner. The test apparatus can be built to model any type of vehicle: a typical sedan, a mid-size sport utility vehicle (SUV), pickup, school bus, etc. The occupant compartment can support complete first and second row seating positions and vehicle interiors. The flexibility of the occupant compartment creates the ability to retro-fit occupant restraint systems and interior components such as side curtains, seat belts, on-board cameras and other data acquisition tools.  
         [0011]     Another advantage of the test apparatus is the elimination of damage to vehicle suspension components which often occur during impacts above 25 mph. The carriage replicates both the leading and trailing sides of the vehicle wheel and suspension compliance. Spring stiffness can be specified individually for each location. The carriage provides a consistent simulation of the ‘curb to wheel’ contact interaction that represents a tripped rollover. The consistency reduces test to test variability.  
         [0012]     The present invention also provides a method of simulating a tripped rollover event of a vehicle with a test apparatus and a cart. The test apparatus comprises a carriage, an occupant compartment, and a rigid shell surrounding the occupant compartment. The method comprises the first step of propelling the test apparatus arranged on the cart at a desired velocity. The next step comprises decelerating the test apparatus on the cart to arrest the movement of the occupant compartment and initiating rotational rollover movement of the occupant compartment. The final step comprises impacting a landing surface with the rigid shell whereby the occupant compartment does not contact the landing surface.  
         [0013]     One advantage of the present invention and method is its capability of representing the occupant compartment transition of lateral vehicle motion into rotational motion commonly seen in laterally tripped laboratory rollover crash tests. The test apparatus rollover event comprises a lateral velocity phase, a lateral deceleration phase, a transition-to-rotation phase, a free-flight phase, and an impact phase. The test apparatus and method provide the ability to provide representative vehicle roll rates, angles, velocities and accelerations and associated occupant motion for lateral tripped rollover crashes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is an elevated side view of a rigid shell and occupant compartment according to the invention;  
         [0015]      FIG. 2  is a top plan view of a rigid shell and occupant compartment according to the invention;  
         [0016]      FIG. 3  is an elevated end view of a rigid shell and occupant compartment according to the invention;  
         [0017]      FIG. 4  is an elevated side view of an upper portion of a rigid shell according to the invention;  
         [0018]      FIG. 5  is a side view of a vehicle compartment according to the invention;  
         [0019]      FIG. 6A  is a top plan view of a bottom platform portion of the rigid shell according to the invention;  
         [0020]      FIG. 6B  is a front elevated plan view of the test apparatus according to the invention;  
         [0021]      FIG. 7  is a perspective view of a test apparatus according to the invention;  
         [0022]      FIG. 8A  a perspective view of a leading edge portion of the carriage according to the invention;  
         [0023]      FIG. 8B  is a perspective view of a trailing edge portion of the carriage according to the invention;  
         [0024]      FIG. 9 a  perspective view of the test apparatus according to the invention;  
         [0025]      FIG. 10  is a perspective view of the test apparatus according to the invention;  
         [0026]      FIG. 11  is a perspective view of the test apparatus according to the invention;  
         [0027]      FIG. 12  is a perspective view of the test apparatus according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     Referring to  FIGS. 1-6   a,  a portion of a test apparatus  10  according to the invention is shown in various views. To maintain consistency throughout this description, the term leading edge shall refer to the side of the test apparatus which will initially experience a tripping impulse. The term trailing edge shall refer to the side of the test apparatus 180 degrees opposite the leading edge. The portion of the test apparatus  10  comprises an occupant compartment  12  and a rigid shell  14 . The rigid shell  14  comprises a top portion  16  and a bottom or platform portion  18 . The occupant compartment  12  is rigidly attached to the platform portion  18  by means of welding or conventional fasteners such as bolts. The occupant compartment  12  represents a portion of the simulated vehicle. The platform portion  18  supports the occupant compartment  12 .  
         [0029]     The occupant compartment  12  can be constructed from a specific vehicle by removing the suspension, power train and fuel system components. As shown, the front end which might contain an engine compartment has been removed. Similarly the rear end which might contain the trunk or storage compartment has been removed. The interior of the occupant compartment  12  can include any relevant interior trim, data collection equipment, restraint systems, or one or more rows of seating positions  19 . Additionally, the interior can include one or more test dummies representative of actual human beings. The occupant compartment  12  is surrounded and protected by the rigid shell  14 .  
         [0030]     The rigid shell  14  helps to prevent deformation to the occupant compartment  12  by transferring the energy of the crash impact to the ground or to a landing surface. The rigid shell  14  comprises metal beams such as steel, supporting a lattice of beams and tubing attached at various locations. The tubes are attached by welding, bolts or other conventional fastening methods. In the alternative, portions of the rigid shell  14  can be detached (not shown) to provide access to the interior of the occupant compartment  12  such as the seating positions  19 , and then reattached prior to testing. The tire geometry of the simulated vehicle is represented by contact pads  22  extending from the bottom of the platform portion of the rigid shell  18 . Additional mass  24  can be mounted to the interior of the rigid shell  14  at discrete locations such as in the front and rear of the rigid shell  14  to compensate for the absence of engine or suspension components. In the alternative, additional mass can be fixed to the exterior surface of the rigid shell  14 . The amount and location of the mass  24  can be chosen to produce the desired test apparatus inertial properties or to simulate the center of gravity of the target vehicle. The dimensions of the rigid shell  14  and mass  24  are important when the test apparatus  10  is used to represent a given vehicle or vehicle type. Overall, the dimensions such as wheel base, tire track width, and various inertial properties of the test apparatus are set for the vehicle being simulated.  
         [0031]     The bottom platform portion  18  of the rigid shell  14  may have a plurality of attachment points  26  for securing the rigid shell. The bottom platform portion  18  can be fitted with adjustable solid masses  24  that can be arranged to allow for adjustment of the appropriate center of gravity for the simulated vehicle.  
         [0032]     Referring now to  FIG. 6B , a front plan view of the test apparatus  10  according to the present invention is shown supported by a cart  28 . The occupant compartment  12  and rigid shell  14  are supported by a carriage  30 . The tire contact pads  22  are each supported by a top surface  33  of the carriage. A cart leading edge  36  extends vertically above a cart top surface  29 . The carriage  30  provides compliance in the horizontal direction and the vertical direction. For example, a spring  32  represents compliance in the horizontal direction between the carriage  30  and the cart  28 . The horizontal spring  32  provides compliance between a leading edge  31  of the carriage  30  and the cart leading edge  36 . Springs  34  represent the vertical compliance between the carriage  30  and the cart  28 . A curb  40  is attached to a leading edge of the carriage  31 . The curb  40  extends vertically above the top surface  33  of the carriage  30  and represents a tripping mechanism for the rigid shell  14 .  
         [0033]     The carriage  30  imitates a suspension by using compliance acting in horizontal and vertical directions to generate a response similar to the replicated vehicle suspension. The compliance characteristics may be determined by calculating the resultant of two springs in series representing the compliance of the actual vehicle suspension and tires. The combination of springs  32 , and  34 , allow for rotation by the occupant compartment  12  about a longitudinal axis. For a single replicated tire/suspension system, the effective vertical spring stiffness is calculated by taking the resultant of two springs in series. In another alternative embodiment of this invention, the front and rear suspensions may be lumped together as one spring by calculating the resultant of two springs in parallel.  
         [0034]     Referring now to  FIG. 7 , a preferred embodiment of a test apparatus  100  is shown. The test apparatus  100  includes an occupant compartment  102  and a rigid shell  104 . The rigid shell  104  comprises a top portion  106  and a bottom or platform portion  108 . The occupant compartment  102  is rigidly attached to the top portion  106  and the platform portion  108  by spot welds  109 . In the alternative, other conventional fasteners such as carriage bolts and nuts, may be used. As shown, the occupant compartment  102  simulates a a portion of a sport-utility vehicle. In the alternative, the occupant compartment  102  may simulate a sedan or sub-compact styled car. The platform portion  108  supports the occupant compartment  102 .  
         [0035]     The rigid shell  104  is comprised of steel rails supporting a lattice of metal beams and tubing attached at various locations. The tubes are attached by welds, bolts or other conventional fastening methods. In the alternative, shell portions  110  of the rigid shell  104  can be detached to provide access to the interior of the occupant compartment  102  or, to adjust the mass or center of gravity. Portions  110  can then be reattached prior to a test. The tire geometry of the simulated vehicle is represented by contact pads  112  on the bottom of the rigid shell  108 . Rigid feet  114  extend vertically below the rigid shell bottom portion to support the rigid shell  104  and form a portion of the contact pads  112 . Shown here, the simulated vehicle has four tire contact pads  112  located near each of the separate corners of the bottom of the rigid shell  108 . The contact pads  112  each interface with the carriage  130 .  
         [0036]     Referring to  FIGS. 7, 8A , and  8 B, the carriage  130  is shown supporting the rigid shell  104  and the occupant compartment  102  at each of the contact pads  112 . The carriage  130  simulates the tires and the suspension of a vehicle and comprises a pair of leading edge portions  132  and a pair of trailing edge portions  134  to support the each of the contact pads  112 .  
         [0037]     The leading edge carriage portions  132  provide compliance in the horizontal and vertical directions. Each of the leading edge portions  132  is comprised of a vertical spring portion  138  and a horizontal spring portion  140 . Each leading edge portion  132  acts independently in the vertical and horizontal directions. A base  142  supports a vertical spring portion  138  is a container structure  144 . The container structure  144  comprises a pair of c-shaped side walls  146 , a bottom plate  148 , and a top plate  150 . A forward portion  151  and rearward portion  153  of walls  146  each contain vertical slots  152  to allow threaded rods  154  to extend from the top plate  150  through the walls  146  and limit the directional motion of the top plate  150 . The threaded rods  154  are secured with conventional fasteners  156 . The spring portion  138  may comprise a coil spring, air shock, pneumatics, or other conventional device used for creating and controlling the vertical compliance.  
         [0038]     The horizontal spring portion  140  is located between a stop structure  160  and a leading edge surface  162  of one of the c-shaped walls  146 . The stop structure  160  is firmly attached to the base  142  and a portion of which extends vertically parallel with surface  162 . The bottom plate  148  of the container  144  is connected to the base  142  such that the container  144  is allowed to move in a translational direction  164  to stress the horizontal spring portion  140 . The spring portion  140  may comprise a coil spring, air shock, pneumatics, or other conventional device used for creating and controlling the horizontal compliance.  
         [0039]     A curb  170  of adjustable height is attached a portion of the container structure  144 . The curb  170  is a vertical flange attached along the leading edge of the carriage  130  and projects vertically above the top surface plate  150  of each of the leading edge carriage portions  132 . The curb  170  is used to generate a tripping impulse. The horizontal and vertical spring portions  138 ,  140  in the leading edge carriage portion  132  can be calibrated to yield a system response representative of a typical vehicle suspension during the roll initiation stages of a crash or rollover event.  
         [0040]     The trailing edge portions  134  provides compliance is the vertical direction. A metal container  180  having vertical walls supports a top plate  182  at a desired test height and orientation. The top plate  182  is fabricated from man made materials such as plywood. In the alternative, a rubber or other manmade material may be substituted. Middle plates  184  may be added or subtracted to change the test orientation of the test apparatus  100 . A layer of recycled tire material  184  provides additional compliance characteristics between the metal pan  180  and the top plate  182 . In the alternative, the trailing edge portion  134  may further include a coil spring, air shock, pneumatics, or other conventional device may be substituted for recycled tire material  184  or used in combination with, for creating and controlling the vertical compliance.  
         [0041]     Referring to  FIG. 9-12 , a preferred embodiment of a method of replicating a vehicle inertial event such as a rollover event using the test apparatus  100  will now be described. The rollover event comprises a lateral velocity phase, a lateral deceleration phase, a transition-to-rotation phase, a free-flight phase, and an impact phase.  
         [0042]     Referring to  FIG. 9 , the lateral velocity phase of the test method of the invention is described. The test apparatus  100  is placed on a moveable cart  184  in a level position. In the alternative, one or more of the middle plates  184  of the trailing edge portion  134  could be added or removed to achieve a non-level stance for the test apparatus  100 . The cart  184  is a conventional unit well known in the art having a support surface  186 , and control means either on-board or located remotely for accelerating and braking the cart. The cart and test apparatus  100  are accelerated until the test apparatus  100  reaches the desired constant velocity.  
         [0043]     Referring to  FIG. 10 , the lateral deceleration phase and the transition to rotation phase of the method for the present invention are described. Once the desired velocity is achieved by the test apparatus  100 , a brake  188  is applied to decelerate the cart  184  causing the test apparatus  100  to experience a lateral deceleration force. The amount of braking force and the time at which the brake is implemented can be specified independently and will determine the deceleration pulse of the test. The deceleration pulse results in a lateral force initiating contact between the test apparatus  100  through that portion of the leading edge portion  132  of the carriage and the curb  170 . The curb  170  “trips” the test apparatus  100  as the momentum transitions into rotational motion of the rigid shell  104  and the occupant compartment  102 .  
         [0044]     Referring to  FIG. 11 , the transition to rotation phase is further described. The rigid shell continues to rotate over the curb  170 . As the rigid shell  104  begins to rotate, the contact pads  112  begins to breakaway from the top surface  150  of the leading edge portion  132 . The contact pads  112  have completely broken away from the top surface  182  of the trailing edge portion  134 .  
         [0045]     Referring to  FIG. 12 , the free-flight phase of the method for the present invention is further described. The rigid shell  104  has completely rotated over the curb  170  and no longer rests on the carriage leading edge or trailing edge portions  132 ,  134  respectively. All contact pads  112  have lifted off the top surfaces  150 ,  182 , respectively. The rigid shell  104  containing the occupant compartment  102  is in rotational free flight.  
         [0046]     Next, the rigid shell  104  experiences an impact phase. The rigid shell  104  comes into contact with an impact pad  188  placed on the ground in the flight path. The impact pad  188  absorbs the energy of the impact of the inertial event or rollover. In a preferred embodiment the impact pad  188  comprises several rubber bladders  189  pressurized to a specified amount arranged symmetrically inside a steel box  190  and covered with plywood  192 . The bladders  189  can be pressurized to give a variety of fixture to ground contact forces. The occupant compartment  102  experiences the impact but is protected by the rigid shell  104  preserving it from destructive damage. The occupant compartment  102  and rigid shell are reusable components that can be tested multiple times.  
         [0047]     The test apparatus  100  and method described produces vehicle motion consistent with a real world tripped rollover crash test. The peak roll rate and roll angle time history were analyzed for one of the trial tests compared to similar tests done with full vehicles. Additional tests were run to determine the repeatability of the test apparatus  100 . Data collected during discrete times of a tripped rollover event indicate high correlation of roll angle and roll rate data when comparing the test apparatus and a full vehicle test.  
         [0048]     In the preferred embodiment shown in  FIGS. 9-12 , the carriage  130  is securely attached to the cart. In an alternative embodiment, the carriage  130  may be positioned loosely on the surface of the cart and the rigid shell contact pads would be securely attached to the carriage  130  instead.  
         [0049]     While particular embodiments of the invention have been shown and described, variations and alternative embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.