Abstract:
A test fixture for rollover crash testing of a test vehicle onto a moving surface employs a cradle to support and rotate the test vehicle. A vertical support structure to position and releasably holds the cradle. A moving sled having a contact surface and is carried by a guide extending beneath the structure and the cradle fixture. The cradle is rotated and released from the structure responsive to a sensor for contact within a drop impact zone on the contact surface of the moving sled. Vertical motion of the cradle is then arrested to prevent further damage to the test vehicle or the test structure.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Application Ser. No. 60/943,355 filed on Jun. 12, 2007 having the same title as the present application and copending with U.S. patent application Ser. No. 11/380,862 filed on Apr. 28, 2006 now U.S. Pat. No. 7,373,801 having the same title as the present application and common inventors. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    This invention relates to an automotive vehicle test fixture. In particular, the invention relates specifically to a fixture to conduct dynamic, repeatable, controlled destructive rollover impact tests of both full scale vehicles and representations to evaluate strength and occupant protection characteristics of the vehicle roof and other vehicle components. The invention provides precise control of initial test parameters including drop height, contact roll rate, contact roll angle, pitch angle, yaw angle, post contact freefall height, vehicle moment of inertia, roadway surface conditions including friction and impact obstructions. In addition, the invention enables the measurement of dynamic forces and orientations between vehicle and road bed and enables multiple tests to be conducted and evaluated on an isolated singular roll-by-roll basis. 
         [0004]    2. Description of Prior Art 
         [0005]    Rollovers have been and continue to be a significant cause of occupant fatalities and serious injuries. To date, the experiments to determine vehicle performance have been criticized as unrepeatable and, thus, inappropriate for vehicle or component design and testing and/or compliance type testing. Various other test fixtures have been developed that addresses some of these issues, but require a large infrastructure to run and do not fully control the vehicle after the first impact and during the test (reference: U.S. Pat. No. 6,651,482). Another device (reference U.S. Pat. No. 6,256,601) articulates about a pivot but does not provide a full rollover capability, nor does it provide a means to simulate a roll about the true roll axis of a vehicle. In addition, none of the other test methods allow for the direct measurement of the loads applied to the vehicle, which are important to evaluating and understanding the dynamics of a rollover event. This subject invention resolves these issues in a manner that will allow effective repeatable vehicle testing. Vehicle testing in the rollover regime is crucial to understanding interactions between the occupant and the vehicle&#39;s structures, restraints, glazing, etc. A better knowledge of these parameters will allow for improved vehicle designs and a safer vehicle fleet. 
         [0006]    Previous testing to determine vehicle performance and vehicle to occupant interactions in rollover conditions uses various types of tests including dropping a rotating vehicle, launching a vehicle from a dolly, launching a vehicle from a ramp or otherwise tripping a vehicle to initiate a roll. The major drawback of these tests is the unrepeatable nature of the testing. While these tests will allow insight into vehicle performance, they do not allow a study of vehicle and component performance during an impact that can be exactly repeated to determine changes in vehicle structure or geometry through repeated tests. In particular, earlier test methods do not result in consistent impacts due to variations in tire to dolly or tire to road impacts before the roof structure interaction or are not controlled after the roof impacts. By controlling the vehicle both before and after the roof impacts, performance during an impact can be isolated and examined in detail. 
         [0007]    U.S. Pat. No. 6,651,482 describes an alternate method of rollover testing. The method described in that patent is considerably different from the invention discussed herein. These differences lead to several shortcomings in the previous methodology including the inability to measure the direct forces on the roof of the vehicle, the inability to control the vehicle after the desired roof contacts, the artificial positioning of anthropomorphic crash test dummies if included, the inability of the system to directly determine the roof crush from the desired impact, the inability to evaluate damage on a per roll and/or cumulative basis. 
         [0008]    U.S. Pat. No. 6,256,601 describes a rollover test sled designed to simulate the behavior of vehicle occupant and safety systems in a rollover accident. The method described differs significantly from the invention presented herein since the test does not provide the means to rotate a test vehicle or dummies about a roll axis. The fixture described also does not provide the means to rotate the test vehicle for the purposes to measure and evaluate vehicle structural integrity. 
         [0009]    Prior art systems are not presently able to provide control of the vehicle in pitch and yaw at the initiation of and during test sequences. 
         [0010]    Copending U.S. application Ser. No. 11/380,862 entitled Vehicle Rollover Crash Test Fixture now U.S. Pat. No. 7,373,801 having common inventors with the present application provides a test fixture for repeatable dynamic vehicle rollover testing. The invention disclosed therein provides a moving sled with a contact surface simulating a roadway or other appropriate medium. A cradle to suspend a test vehicle is equipped to rotate and release the vehicle onto the contact surface to repeatably simulate a rollover condition. While coupled motion of the sled and rotation of the vehicle prior to impact provide repeatable test results with highly accurate simulation, the structural and system requirements for creating and coordinating the moving sled contact zone are complex and costly. It is therefore desirable to provide a rollover test fixture with the capabilities of the prior system but simplified to reduce cost, complexity and simulation error as well as ease of setup and safety of operating personnel. 
         [0011]    The present invention addresses these issues and provides a simplified and improved dynamic, repeatable vehicle rollover test fixture. 
       SUMMARY OF THE INVENTION 
       [0012]    A test fixture for rollover crash testing of a test vehicle incorporates a cradle to support and rotate a test vehicle. The cradle is carried by a structure to position and releasably hold the cradle. A sled having a contact surface simulating a roadway is carried on a bearing assembly extending beneath the structure and the cradle fixture. The cradle, with the supported vehicle, is rotated at a predetermined rate to simulate the initial contact velocities for a rollover event and released from the structure responsive to a sensor for contact on a drop impact zone on the contact surface. The bearing supported sled reacts to the impacting vehicle and is displaced along the bearing assembly. The vertical motion of the cradle is arrested at the event completion to avoid damage to the bearing and sled system as well as limiting further damage to the test vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]    The elements and features of the invention are further described with respect to the detailed description herein and the following drawings wherein 
           [0014]      FIG. 1  is a front view of the rollover fixture showing the major components; 
           [0015]      FIG. 2  is a side view of the rollover fixture of  FIG. 1 ; 
           [0016]      FIG. 3  diagrams an embodiment of an electrical control system used to manually start the rollover test process and to enable actuation of vehicle drop; 
           [0017]      FIG. 4  diagrams an embodiment of a data acquisition system used to monitor and record dynamic physical responses of the vehicle, roadway and dummies within the vehicle; 
           [0018]      FIG. 5  is a front isometric view of an alternative embodiment of the invention with a four post support structure; 
           [0019]      FIG. 6A  is an isometric view of structural details of an implementation of the alternative embodiment in a squared orientation; 
           [0020]      FIG. 6B  is a side view of the structure of  FIG. 6A ; 
           [0021]      FIG. 6C  is an end view of the structure of  FIG. 6A ; 
           [0022]      FIG. 7A  is an isometric view structural details of an implementation of the alternative embodiment in a nose-down and yawed orientation; 
           [0023]      FIG. 7B  is a side view of the structure of  FIG. 7A ; 
           [0024]      FIG. 7C  is an end view of the structure of  FIG. 7A ; and, 
           [0025]      FIG. 8  is an isometric view of a gantry capability added to the embodiment of  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    An exemplary embodiment of the structure of the present invention is illustrated in  FIGS. 1 and 2 . The test fixture  100  incorporates a sled  110  supported by a bearing system  112  having guide rails  114  and caged roller bearings  116  for the embodiment shown. Drop tower assembly  118  includes a front drop column  120  and a rear drop column  122  connected overhead by a cross beam  124 . The drop tower assembly  118  straddles the sled guide rails  114  and the drop columns are mounted to yaw adjustment guide plates  126  that are pivotably fastened to a floor  102  of the test area. The angular orientation of the drop tower assembly relative to the sled guide rails therefore sets the yaw position of the test vehicle. The drop columns  120  and  122  each support vertical guide bearings  128 . Runner assemblies  130  which support and couple to a vehicle cradle  132  ride on the guide bearings for vertical motion of the cradle. The vehicle cradle is fitted with various brackets to facilitate mounting of various models of full size test vehicles  104  or test bucks. For the exemplary cradle shown in this embodiment, the attachment of the vehicle to the cradle is accomplished by removing the bumpers of the vehicle and attaching the cradle cross members to the bumper attachment structure on the vehicle. Cradle ballast weights  134  may be also affixed to the vehicle or cradle in order to compensate or adjust the vehicle moments of inertia. 
         [0027]    The sled is movable on the bearing system along the guide rails in reaction to the impact of the vehicle. For the embodiment shown in the drawings, a roadway surface  136  is mounted to the upward face of the sled in order to simulate a road condition for impact with the vehicle. Various road surface materials are employed to simulate various real road conditions including Macadam and concrete. In alternative embodiments, various other surface features are mounted to the sled structure such as curb elements  137  as shown in  FIG. 2  for impact studies. 
         [0028]    With the sled simulating the roadway for impact of the vehicle, rotation of the vehicle cradle establishes the simulation parameters for impact of the vertically descending vehicle with the roadway. A rotation drive assembly  138  located adjacent the front drop column provides a rotation drive motor support frame  140  that supports a rotation drive gear motor  142 . A rotation drive support shaft  144  couples the rotation drive motor and the vehicle cradle. The drive support shaft incorporates universal joints  146  that provide angular alignment between the drive motor and the vehicle cradle. Slide rods  148  couple the vehicle cradle to the runner assemblies. A clutch assembly  150  connecting the gear motor to the drive support shaft allows the motor to be disengaged during the impact sequence. The sled reacts to the impact of the rotating vehicle, moving along the bearing assembly to allow the rolling motion of the vehicle to continue while remaining supported by the cradle on the vertical columns. 
         [0029]    For the embodiment shown, a sled decelerator  152  located at the end of the sled guide rails  114  is provided to beneficially decelerate and stop the sled in a controlled manner at the end of its travel in reaction to the rotational inertia of the impacting vehicle. 
         [0030]    At the completion of the roll-over impact event, the car body or buck is arrested to prevent damage to the support elements of the fixture or the sled or drive system through unwanted contact. To accommodate this requirement, a vertical brake assembly  154 , best seen in  FIG. 1 , is provided as a portion of the vertical runner assembly. The vertical brake engages a rail element  156  on the drop towers on each side of fixture. For the embodiment shown in the drawings the vertical brake is a disc brake assembly acting on the rail. The brake is actuated by a sensing element. In exemplary embodiments, a contact switch  158  on the guide rail senses motion of the sled and actuates the brake. Alternatively, event completion is determined by the angle of rotation of the vehicle under test or predetermined timing and sensing of the completed event is accomplished based on the rotation angle of the support shaft elements in the vertical runner assemblies. An index pin on the slide rod which engages a micro switch upon rotation through a predetermined arc or an angular rotation sensor on the axle or the rotation drive pulley is employed as the event completion sensor. 
         [0031]      FIG. 3  is a diagram of a simplified electrical control system. Since human safety is paramount concern while conducting vehicle testing, system power is enabled by a key-switch  160 . A start switch  162  is manually actuated to initiate the test sequence that causes control relay  164  to close and thereby energizing the motor  142  under the control of motor control circuit  166 . Upon energizing the motor control relay, rotation of the cradle is initiated. Control circuit  166  controls current to the gear motor to achieve the desired rotational velocity within a predetermined rotation angle for drop. As the cradle passes a rotation angle sensor  168 , the front drop actuator  170  and rear drop actuator  172  are energized to release thereby allowing the vehicle cradle  132  and the subject test vehicle  104  it contains to drop. In the embodiment shown, power is removed from the gear motor responsive to the rotation angle sensor by resetting (opening) the motor power relay. Upon actuation of the event complete switch  158  the vertical brake assemblies  154  are activated and a rotation brake  174  is activated to stop rotation of the cradle. As shown in  FIG. 3 , additional test equipment features such as illumination lights  176  for cameras  178  are controlled by a switch  180  located on the operator controls. 
         [0032]    As shown in  FIG. 4 , a suite of instrumentation sensors is incorporated to measure and record the dynamic physical responses of the vehicle during the test. Sensors included in a preferred embodiment of the invention are: encoders  182  and  183  respectively mounted to the front and rear drop columns  120  and  122  for recording vertical motion of the cradle and supported vehicle; encoder  184  is used to monitor the X axis linear position to derive speed and acceleration of sled  110 ; load cells  193  arranged between the roadway surface and the sled to monitor Z-axis impact forces imposed by the test vehicle; load cells  185  arranged between the roadway surface and the sled to monitor X-axis impact forces imposed by the test vehicle; encoder  186  to monitor the roll orientation of the test vehicle; accelerometers  187  to monitor impact forces imposed upon a test dummy; sensors  188  to monitor displacements imposed upon a test dummy during the test; accelerometers  189  to monitor impact forces imposed upon the test vehicle; sensors  190  to measure displacements imposed upon the test vehicle; cameras  182  mounted about the rollover apparatus to monitor various external aspects of the test vehicle; and cameras  183  mounted within the test vehicle to monitor various internal aspects including roof crush intrusion and dummy positions during the test. 
         [0033]    As shown in  FIG. 4 , the suite of sensors as previously described are preferentially input to signal conditioning electronics  191  and digitized for input to a data acquisition computer  192 . Once digitized, the collected data is saved, analyzed and formatted for various studies and reports. 
         [0034]    An alternative embodiment of the present invention which employs an four post structural support arrangement for simplified operation of the system in positioning the vehicle for pitch and yaw control in the test is shown in  FIG. 5  and with structural details of an exemplary embodiment in  FIGS. 6A-7C . A four post structure having vertical supports  502   a - 502   d  on which horizontal support beams  504   a  and  504   b  are mounted provides flexibility in positioning a suspension beam  506  from which the test vehicle  104  is suspended with a cradle  508  as will be described in greater detail with respect to  FIGS. 6A-6C . By adjusting the elevation of the vertical supports, the horizontal support beams provide an angled mounting of the suspension beam to create a desired pitch angle of the vehicle mounted in the cradle. Additionally, movement of the suspension beam mounting along the horizontal support beams creates an adjustable yaw angle for the vehicle. A control beam  510  with opposing control arms  512   a  and  512   b  extending for engagement of the cradle maintain the yaw angle of the cradle and supported vehicle during the drop as will be described in greater detail with respect to  FIGS. 7A-7C . 
         [0035]    A detailed implementation of the structure of  FIG. 5  is shown in  FIGS. 6A-6C . Vehicle cradle  508  is suspended from suspension beam  506  with drop rods  514   a  and  514   b  which are attached to rotational support bosses  516   a  and  516   b  at opposite ends of the cradle. The cradle rotates between the support bosses for positioning of the vehicle and inducing the angular rotation of the vehicle for the appropriate test protocol as previously described. The drop rods extend through slip bearings in actuation assemblies  518   a  and  518   b  which function in a manner similar to guide bearings on the drop columns as described with respect to the first embodiment. The actuation assemblies additionally include a brake to capture the drop rods for vertical capture of the cradle and vehicle at the conclusion of the test to arrest further vertical motion as previously described. 
         [0036]    Control beam  510  is carried by structural supports  520   a  and  520   b  which are in turn carried on horizontal beam elements  522   a  and  522   b . For the embodiment shown, the horizontal beam elements are attached to secondary vertical supports  524   a ,  524   b ,  524   c  and  524   d . Structural supports  520   a  and  520   b  are movably positionable on the horizontal beam elements to allow angular positioning of the control beam to match the yaw angle of the suspension beam thereby maintaining the geometric relationship of the control arms with respect to the vehicle cradle for control of lateral motion during the vehicle drop and arrest. 
         [0037]    For the embodiment shown, vertical supports  502   a - d  incorporate telescoping adjustment elements  526   a - 526   d  for vertical adjustment of horizontal support beams  504   a  and  504   b . Similarly, secondary vertical supports  524   a - 524   d  may incorporate telescoping elements to vertically position the horizontal beam elements and associated structural supports  520   a  and  520   b  for matching pitch angle of the control arm and the suspension beam. 
         [0038]    Vehicle cradle  508  provides attachment plates  530  for direct engagement of the wheel attachment bolts on the vehicle through holes  532 . By removing the wheels and engaging the attachment plates the vehicle is directly supported by the cradle without modification to the vehicle. Additionally, the engagement by the cradle in this manner avoids any unintended structural stiffening of the vehicle which may occur with direct engagement of the cradle with structural elements of the vehicle body or frame. However, locking structure to secure the vehicle suspension is employed where required to assure that compliance of the suspension does not affect the input forces on the vehicle. 
         [0039]      FIGS. 7A-7C  provide isometric, side and end views of the second embodiment with the pitch and yaw of the vehicle cradle modified from the orthogonal settings. In the views shown, the cradle is pitched tail down (as opposed to nose down as shown in  FIG. 5 ) by extending the telescoping adjusting elements  526   c  and  526   d  to raise support beam  504   b  and lowering the telescoping adjusting elements  526   a  and  526   b  to lower support beam  504   a . This support arrangement places suspension beam  506  at a first pitch angle relative to the plane of the sled for impact. Similarly, a yaw angle induced by sliding the ends of suspension beam  506  in opposite directions; forward along support beam  504   a  and rearward along support beam  504   b . This places the cradle in a yawed position with respect to the directional axis of the sled. The control beam is similarly yawed by moving supports  520   a  and  520   b  along second horizontal support beams  522   a  and  522   b . The angle of the control beam positions control arms  512   a  and  512   b  to maintain the yaw angle of the cradle during the drop in which slip rods  514   a  and  514   b  slide through actuation assemblies  518   a  and  518   b.    
         [0040]      FIG. 8  shows an additional feature of the present invention in which vertical supports  502   a - 502   d  each incorporate a support block  560  adjacent the foot of the support. A retractable wheel  562  is supported from the block to provide lateral motion of the entire cradle support assembly for lateral motion along tracks  564  as a gantry allowing loading of test vehicles into the cradle at a location separated from the sled track. This provides additional safety for personnel operating the system and simplifies pre and post test support. 
         [0041]    For the embodiment shown in  FIG. 5 , the sled incorporates three separable structures center  10   a,  right wing  10   b  and left wing  10   c.  The sled may be operated with all three elements interconnected to obtain data for all potential contact points, i.e. the roof and support pillars, front hood/fender and rear contact. Operation of the center only allows data gathering with respect to the strength of the roof and support pillars only, for example, with the right and left wings not connected and therefore not providing any contact surface for the nose and tail of the test vehicle. Operation of the center with one or the other of the wings allows data gathering for the nose and tail structures. 
         [0042]    Rotation of the cradle is imparted in the alternative embodiment using a gear motor or similar drive element as previously described mounted in one or both of the rotational support bosses. Alternatively, a motor driven drive pulley  546  engages a cable  548  which runs a rotational sleeve on the control beam to pulleys  550   a  and  550   b  at the attachment of the control arms to reaction pulleys  552   a  and  552   b  mounted on the rotational support bosses. 
         [0043]    Alternatively, the cable provided for the pulley can be interconnected to the sled and pneumatic power provided for driving motion of the sled. Motion of the sled thereby imparts rotational motion to the cradle. By attachment of the cable to pulleys  552   a  and  552   b  using end beads captured in slots in the pulley wall, the cable is released from the pulley at the desired rotation providing free rotation of the cradle at the actual impact. 
         [0044]    Having now described the invention in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present invention as defined in the following claims.