Abstract:
A Guided Soft Target (GST) system and method provides a versatile test system and methodology for the evaluation of various crash avoidance technologies. This system and method can be used to replicate the pre-crash motions of the CP in a wide variety of crash scenarios while minimizing physical risk, all while consistently providing a sensor signature substantially identical to that of the item being simulated. The GST system in various example embodiments may comprise a soft target vehicle or pedestrian form removably attached to a programmable, autonomously guided, self-propelled Dynamic Motion Element (DME), which may be operated in connection with a wireless computer network. Specific geometries for the DME have been discovered that minimize the risk of the DME flipping up and hitting or otherwise damaging or disrupting the ride of typical test vehicles during impact of the test vehicles with the GST, all while minimizing the effect of the DME on the sensor signature of the GST.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to systems and methods, including guided soft targets, for testing crash avoidance technologies. 
       BACKGROUND 
       [0002]    As Advanced Crash Avoidance Technologies (ACATs) such as Forward Collision Warning (FCW), Crash Imminent Braking Systems and other advanced technologies continue to be developed, the need for full-scale test methodologies that can minimize hazards to test personnel and damage to equipment has rapidly increased. Evaluating such ACAT systems presents many challenges. For example, the evaluation system should be able to deliver a potential Collision Partner (CP) reliably and precisely along a trajectory that would ultimately result in a crash in a variety of configurations, such as rear-ends, head-ons, crossing paths, and sideswipes. Additionally, the collision partner should not pose a substantial physical risk to the test driver, other test personnel, equipment, or to test vehicles in the event that the collision is not avoided. This challenge has been difficult to address. Third, the Collision Partner (CP) should appear to the test vehicle as the actual item being simulated, such as a motor vehicle, a pedestrian, or other object. For example, the CP should provide a consistent radar reflection signature to the various test vehicles, substantially identical to that of the item being simulated. While radar is a common sensor used in ACAT systems, several other sensors may be used in ACATs including lasers, sonar, and infra-red and visual image cameras. The point is that the CP should appear to the test vehicle sensor as the actual vehicle, person or object being simulated. 
       SUMMARY 
       [0003]    A Guided Soft Target (GST) system and method are provided that overcome these challenges and more by providing a versatile test system and methodology for the evaluation of various crash avoidance technologies. This system and method can be used to replicate the pre-crash motions of the CP in a wide variety of crash scenarios while minimizing physical risk, all while consistently providing a sensor signature substantially identical to that of the item being simulated. The GST system in various example embodiments may comprise a soft target vehicle or pedestrian form removably attached to a programmable, autonomously guided, self-propelled Dynamic Motion Element (DME), which may be operated in connection with a wireless computer network. The Soft Car or Soft Pedestrian is intended to be a realistic representation of a CP for both the driver and the system under evaluation, and the DME serves as a means of conveyance for the Soft Car such that the motions of the CP are realistic. As a fully autonomous vehicle, the GST can operate in several modes. It can be programmed to coordinate its motions with the subject vehicle during the pre-crash phase such that the initial conditions of the crash phase are replicated from run to run. It can also be programmed to follow a predetermined trajectory in which position and speed are specified as functions of time to a target ground-fixed impact point; or operate in a mixed mode where the GST coordinates its motions with the subject vehicle during the initial phase of the event, and switches to a predetermined trajectory in which position and speed are specified as functions of time at the instant that the ACAT or subject vehicle driver begins to respond to the conflict. This enables the analyst to determine the effect of the ACAT system on the subject vehicle&#39;s potential impact with, or avoidance of, the GST as it arrives at the target impact point (e.g., the change in such indices as the “resultant relative velocity at minimum distance” (RRVMD), minimum distance (MD), etc.). Additionally, specific geometries for the DME have been discovered that minimize the risk of the DME flipping up and hitting or otherwise damaging or disrupting the ride of typical test vehicles during impact of the test vehicles with the GST, all while minimizing the DME&#39;s visibility to the test vehicle&#39;s sensor(s), and thereby minimizing the effect of the DME on the sensor signature of the GST. 
         [0004]    The developed car and pedestrian GST system has versatile as well as robust capabilities, and provides test engineers with the flexibility and low test cycle time necessary for development and testing of ACATs. The GST system can replicate virtually any type of collision between the GST and the subject vehicle, including rear-ends, head-ons, crossing paths, sideswipes and pedestrian collisions. The Soft Car or Soft Pedestrian bodies can be constructed with a wide variety of three-dimensional shapes and sizes, allowing the ACAT developer or evaluator to measure the effect of the system across a range of collision partners. These collision partner soft bodies can be re-used and reassembled quickly (usually within 10 minutes), and the self-propelled-and-guided Dynamic Motion Element (DME), encased in a hardened, low-profile, drive-over shell, can be quickly repositioned, allowing the test team to evaluate large numbers of different, realistic scenarios with multiple repeats. 
         [0005]    The development of a test methodology, based on the GST system, allows for the evaluation of diverse ACATs covering a wide range of crash and pre-crash conflict scenarios, effectively exercising the various modes and operating conditions of the ACAT. The ability to guide and propel a conflict partner on complex trajectories through the time of collision enables the evaluation of not only collision avoidance but also collision mitigation technologies. Further, the data collected for both the subject vehicle and GST in the course of such evaluations allows detailed analysis of system response and effectiveness, including its effects on collision avoidance (i.e., minimum distance) as well as its effects on collision severity (i.e., closing speed, contact points, relative heading angle) when a collision occurs. 
         [0006]    The inventors are unaware of any prior methods or test systems in which the collision partner moves autonomously, with precise control, realistically, at relatively high speeds up to and through the point of impact, and can collide with a subject vehicle at relatively high collision speeds, while minimizing physical risk to test personnel, the subject vehicle, the collision partner, and other equipment. Further, the specific geometries for the DME that have been found to increase operational safety while minimizing sensor signature are believed to be new and nonobvious. Other aspects of the invention are disclosed herein as discussed in the following Drawings and Detailed Description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The invention can be better understood with reference to the following figures. The components within the figures are not necessarily to scale, emphasis instead being placed on clearly illustrating example aspects of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views. It will be understood that certain components and details may not appear in the figures to assist in more clearly describing the invention. 
           [0008]      FIG. 1  is a top isometric view of an example Dynamic Motion Element (DME) according to various example embodiments. 
           [0009]      FIG. 2  is a bottom isometric view of the example Dynamic Motion Element (DME) of  FIG. 1  according to various example embodiments. 
           [0010]      FIG. 3  is a top plan view of the example Dynamic Motion Element (DME) of  FIG. 1  according to various example embodiments. 
           [0011]      FIG. 4  is a left side elevation view of the example Dynamic Motion Element (DME) of  FIG. 1  according to various example embodiments. 
           [0012]      FIG. 5  is a back side elevation view of the example Dynamic Motion Element (DME) of  FIG. 1  according to various example embodiments. 
           [0013]      FIG. 6A  is a front perspective view of an example light passenger vehicle Guided Soft Target (GST) according to various example embodiments. 
           [0014]      FIG. 6B  is a back perspective view of the example light passenger vehicle Guided Soft Target (GST) of  FIG. 6A  according to various example embodiments. 
           [0015]      FIG. 6C  is a side elevation view of the example light passenger vehicle Guided Soft Target (GST) of  FIG. 6A , shown before being impacted by an example Subject Vehicle (SV), according to various example embodiments. 
           [0016]      FIG. 6D  is a side elevation view of the example light passenger vehicle Guided Soft Target (GST) of  FIG. 6A , shown while being impacted by an example Subject Vehicle (SV), according to various example embodiments. 
           [0017]      FIG. 7  is a front perspective view of an example pedestrian Guided Soft Target (GST) according to various example embodiments. 
           [0018]      FIG. 8  is a diagram showing certain elements of an example Guided Soft Target (GST) system architecture according to various example embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Following is a non-limiting written description of example embodiments illustrating various aspects of the invention. These examples are provided to enable a person of ordinary skill in the art to practice the full scope of the invention without having to engage in an undue amount of experimentation. As will be apparent to persons skilled in the art, further modifications and adaptations can be made without departing from the spirit and scope of the invention, which is limited only by the claims. 
       Definitions 
       [0020]    The following acronyms will be used throughout this description: Advanced Crash 
         [0021]    Avoidance Technologies (ACATs); Guided Soft Target (GST); Dynamic Motion Element (DME); Forward Collision Warning (FCW); Crash Imminent Braking Systems (CIBS); Collision Partner (CP); Resultant Relative Velocity at Minimum Distance (RRVMD); Minimum Distance (MD); Wireless Local Area Network (WLAN); Guidance, Navigation and Control (GNC) computations; Differential GPS (DGPS); Ground Clearance (GC). 
         [0022]    Dynamic Motion Element 
         [0023]    The Dynamic Motion Element (DME)  100 , examples of which are shown in  FIGS. 1-5 , is at the heart of the GST system. The DME  100  is a completely self-contained, un-tethered, relatively high-speed, mobile platform for the soft car  600 , which performs all Guidance, Navigation and Control (GNC) computations, and is capable of being driven over by the subject vehicle  650  without damage to itself or the subject vehicle  650 . 
         [0024]    Positional measurements, which are the primary measurement used in typical GNC computations, are achieved via the on-board DGPS receiver. Other inputs to the GNC computations may include the yaw rate, as measured by a yaw rate sensor or inertial measurement unit, and heading angle, as measured by an electronic compass. 
         [0025]    The DME  100  may incorporate a pair of brushless DC motors to drive, for instance, the rear wheel(s)  220 , while steering of the front wheel(s)  200  may be accomplished via a brushless DC position control servo, for example. Wheels  200 ,  220  means the wheel assembly, including the tire or other material that contacts the ground. Front and/or rear brakes, such as disc brakes, may provide braking capability during a conflict scenario or to bring the DME  100  to a stop after a scenario. The brakes may be actuated autonomously by the DME  100  according to a pre-programmed trajectory or by a test engineer via a radio transmitter in order to perform an emergency-stop, for example. 
         [0026]    The construction of the DME  100  facilitates mounting, housing and protection of all system components, including for example the computer, sensors, actuators, batteries, and power supplies. The DME  100  may be constructed primarily of aluminum, steel, or any suitably strong material(s), and may utilize an egg-crate, honeycomb, or similar type internal structure (not shown) with exterior armor cladding. With reference to  FIG. 1 , the DME  100  may include a front side  75 , a rear or back side  70 , a left side  80  (which would be a driver&#39;s side if the DME was an automobile in the U.S.), and a right side  85  (which would be a passenger&#39;s side if the DME was an automobile in the U.S.). The exterior armor cladding may comprise a top surface  10  and a bottom surface  20  (shown in  FIG. 2 ), a front upper surface  40 , a rear upper surface  30 , a left side upper surface  50 , and a right side upper surface  60 . Other or fewer surfaces may be employed in various other embodiments. As shown in  FIG. 2 , wheels may extend downward below bottom surface  20 . In one example embodiment, wheels may comprise one or more non-steered wheels  220  and one or more steered wheels  200 . Any or all of the wheels may be steered, and any or all of the wheels may be driven. In one example embodiment discussed herein, the rear wheels  220  (which may comprise two wheels adjacent to each other) are driven and the front wheels  200  are steered, that is, at least partially rotatable about a substantially vertical axis (i.e., an axis substantially perpendicular to bottom surface  20 ). 
         [0027]    As illustrated in the example embodiments shown in  FIGS. 3 ,  4  and  5 , the large horizontal dimensions L, W, and small height H of DME  100  create shallow approach angles α 1 , α 2 , minimizing the load imparted horizontally when driven over by the subject vehicle  650 , for instance as shown in  FIG. 6D . These dimensions also minimize the potential for contact between the subject vehicle  650  structure (e.g., undercarriage or bumpers) and the DME  100  structure, for instance by the DME flipping up against the subject vehicle  650  when the GST is impacted by the subject vehicle  650 . 
         [0028]    With reference to  FIG. 3 , to avoid “flip up” of the DME  100  under the subject vehicle  650 , dimension L may optimally be selected to be greater than or equal to the wheelbase of the typical subject vehicle  650  (i.e., the distance from the centerline of the front axle to the centerline of the rear axle of the subject vehicle  650 ). To minimize the effect of the DME  100  on the sensor signature of the GST, dimension L may be selected to be less than the overall length of the soft body  600 . In a first embodiment, dimension L may be selected to be about 2000 millimeters, plus or minus 300 millimeters, for instance for use with smaller vehicles. In a second embodiment, dimension L may be selected to be about 2600 millimeters, plus or minus 300 millimeters, for instance for use with larger vehicles. In a third embodiment, dimension L may be selected to be about 3200 millimeters, plus or minus 300 millimeters, for instance for use with long vehicles. In a fourth embodiment, dimension L may be selected to be about 4000 millimeters, plus or minus 500 millimeters, for instance for use with very long wheel-base vehicles such as crew cab long bed pick-up trucks. 
         [0029]    Also to avoid “flip up” of the DME  100  under the subject vehicle  650 , dimension W may optimally be selected to be greater than or equal to the track width of the typical subject vehicle  650  (i.e., the distance from the centerline of the driver&#39;s side tires to the centerline of the passenger&#39;s side tires of the subject vehicle  650 ). To minimize the effect of the DME  100  on the sensor signature of the GST, dimension W may be selected to be less than the overall width of the soft body  600 . In the first embodiment, dimension W may be selected to be about 1200 millimeters, plus or minus 300 millimeters, for instance for use with smaller vehicles. In the second embodiment, dimension W may be selected to be about 1800 millimeters, plus or minus 300 millimeters, for instance for use with larger vehicles. In the third and fourth embodiment, dimension W may be selected to be about 2600 millimeters, plus or minus 500 millimeters, for instance for use with very large vehicles such as heavy trucks. 
         [0030]    Any other lengths for dimensions L and W may be used as long as they are coordinated with each other and dimension H to result in angles α 1 , α 2 , falling within appropriate ranges, discussed below. For example, in the example embodiments shown in  FIGS. 6A-6D  in which the subject vehicle  650  was a late model Honda Accord, dimension L was selected to be about 2790 millimeters, dimension W was selected to be about 1520 millimeters, and H was selected to be about 130 millimeters (plus or minus 10 millimeters). Dimensions L and W can be smaller than the first embodiment where the GST is a smaller object such as a pedestrian  700 , such as in the example DME  100 ′ shown in  FIG. 7 . Finally, dimensions L and W could be scaled up beyond those provided in the fourth embodiment to work with even larger subject vehicles  650 . 
         [0031]    With reference to  FIGS. 4 and 5 , H is the vertical dimension from the ground  400  (ground  400  meaning the surface of the road or other surface on which the DME  100  travels) to the top 10 of DME  100 . To minimize the ride disturbance to the subject vehicle  650 , H is preferably as small as possible. Minimizing H tends to prevent discomfort to drivers and potential accidents, and minimizes chances of damage to the subject vehicle  650  or instrumentation attached thereto, airbag deployment, and the like. H is also preferably minimized to prevent the chance of the DME  100  striking the bottom of the subject vehicle  650  even when the DME  100  does not “flip up.” Minimizing H requires minimizing Ground Clearance (GC). The Ground Clearance or GC of the DME  100  is the vertical distance from the ground  400  to the bottom  20  of DME  100 . Nominal Ground Clearances that have been found to work acceptably include distances of about 12 to 19 millimeters, and at least about 5 millimeters but preferably no more than 50 millimeters. This GC helps to avoid “flip up” of the DME  100  under the subject vehicle  650 . In the embodiments described herein H has been minimized to about 130 millimeters, plus or minus 10 millimeters. Using other materials and smaller components could potentially reduce H even further. In addition to these dimensions, the edge thickness of the DME  100 , shown at position  90 , may be less than 30 millimeters, again to minimize the radar or other sensor signature of the DME  100 . 
         [0032]    H is minimized not only to minimize ride disturbance of the subject vehicle  650  and to prevent contact of the DME  100  to the undercarriage of the subject vehicle  650 , but H is also selected to coordinate with dimensions L and W so that angles α 1 , α 2 , are minimized and fall within appropriate ranges. As shown in  FIG. 4 , angle α 1  is the angle between the ground  400  and the upper back surface  30  of the DME  100 , or between the ground  400  and the upper front surface  40  of the DME  100 , or both. In typical embodiments angle α 1  is the same for both the front and back upper surfaces,  30 ,  40 , of DME  100 , however, angle α 1  can differ between the front and rear the upper surfaces,  30 ,  40 , of the DME  100  if the upper surfaces of DME  100  are not symmetrical about a central latitudinally-extending vertical plane. As shown in  FIG. 5 , angle α 2  is the angle between the ground  400  and the upper left side surface  50  of the DME  100 , or between the ground  400  and the upper right side surface  60  of the DME  100 , or both. In typical embodiments angle α 2  is the same for both the left and right upper surfaces,  50 ,  60 , of DME  100 , however, angle α 2  can differ between the left and right upper surfaces,  50 ,  60 , of the DME  100  if the upper surfaces of DME  100  are not symmetrical about a central longitudinally-extending vertical plane. Importantly, while upper surfaces  30 ,  40 ,  50  and  60  are shown as substantially flat planes each comprising multiple panels, any or all of upper surfaces  30 ,  40 ,  50  and  60  may be curved and not flat, or partially curved and partially flat. Where any or all of upper surfaces  30 ,  40 ,  50  and  60  are curved and not flat, or are partially curved and partially flat, angles α 1 , α 2 , may be measured between the ground  400  and the steepest portion of any of corresponding upper surfaces  30 ,  40 ,  50  and  60 . For purposes of this measurement the steepness or angle of a curve at a given point is measured by a line tangent to the curve at that point, i.e., the first derivative thereof, as is known in the art. 
         [0033]    Like H, angles α 1 , α 2 , are minimized to minimize ride disturbance of the subject vehicle  650  and to make the subject vehicle  650  travel as smoothly as possible over the DME  100 . In various embodiments α 1  and α 2  may each be selected to be less than about 45 degrees, and preferably less than 15 degrees. In one example embodiment α 1  is selected to be about 5 degrees while α 2  is selected to be about 13 degrees. 
         [0034]    ACATs use various types of sensors to detect obstacles in the path of the subject vehicle  650 , and to alert the driver or take evasive action or some other action if the ACAT determines that the subject vehicle is likely to collide with such an obstacle. Accordingly, these sensor systems have often been designed not to be triggered by items normally in the roadway, such as raised manhole covers and highway construction plates, or at least distinguish between such items close to the roadway and larger items, such as another vehicle. Still, some ACAT systems may trigger an alarm or some other type of response if they detect something in the roadway as large as a DME  100 . For this reason, it has been discovered to be important to minimize the sensor signature of the DME  100 . Additionally, to achieve accurate results when testing ACATs against GSTs that simulate objects such as vehicles, pedestrians, or other objects, it is helpful to minimize the distortion of the sensor signature of the simulated vehicle, pedestrian, or other object that is caused by the presence of the DME  100 . For this separate reason it has been discovered to be important to minimize the sensor signature of the DME  100 . 
         [0035]    The geometries disclosed herein for DME  100  have been found to effectively minimize the sensor signature of the DME  100 . While all of the geometries disclosed above are useful for minimizing the sensor signature of the DME  100 , it has been discovered that the following characteristics are individually and together particularly helpful in minimizing the sensor signature of the DME  100 : H less than about 350 millimeters, and preferably not more than about 300 millimeters; α 1  and α 2  not more than about 45 degrees, and L and W dimensions within the corresponding length and width dimensions of the soft car  600  (shown in  FIGS. 6A-6D ) or other item that is mounted to the DME  100  to create the GST. For example, for a typical soft car  600  the L and W dimensions may be not more than about 4880 millimeters for L and about 1830 millimeters for W. Other L and W dimensions may be appropriate for other GSTs, as will be apparent to persons of skill in the art upon reviewing this disclosure. 
         [0036]    The DME  100  may also employ retractable running gear, such that the structure “squats” onto the road surface when driven over by the subject vehicle  650 . This creates a direct load path from the tires of the subject vehicle  650  to the ground  400  without passing through the GST wheels  200 ,  220  and associated suspension components. This may be accomplished through the use of pneumatic actuators that create just enough force to deploy the wheels  200 ,  220  and lift the DME  100  to its maximum ground clearance, for instance approximately one centimeter. In these embodiments the DME structure  100  can squat passively under the loading of the tires of the subject vehicle  650 , without requiring dynamic actuation. 
         [0037]    Soft Car 
         [0038]    The soft car  600  as shown in  FIGS. 6A through 6D  is removably mounted atop the DME  100  and is designed to minimize the potential for damage to the body panels of the subject vehicle  650  that impacts the soft car body  600 . The soft car body  600  can be designed to replicate the three-dimensional shape, appearance and size of various objects, such as light passenger vehicles. It may be constructed completely from “soft” materials, such as polyethylene foam, hook-and-loop closure and flexible epoxy, for instance. The panels of the soft car body  600  and internal structure may be fabricated completely from light-weight, flexible and durable polyethylene foam, and may be connected to each other and to the DME  100  top surface by way of hook-and-loop or similarly functioning material. This minimizes the risk of tearing individual panels, and also allows for quick reassembly after a collision with the subject vehicle  650 . The internal structure of the soft car  600  may be made up of bulkheads that interconnect to form a framework for the outer skin panels. These bulkheads can provide enough structural support for the body panels under higher speed aerodynamic loading but are light and flexible relative to the subject vehicle  650 , thereby minimizing the load imparted to the subject vehicle  650  body panels in the event of a collision. Instead of a soft car  600  as shown in  FIGS. 6A through 6D , any other shape may be attached to the DME  100  to form a GST, such as an inflatable pedestrian shape  700 , as shown in  FIG. 7 , or such as an inflatable vehicle shape. 
         [0039]    Example System Architectures and Functions 
         [0040]    GST systems in various example embodiments may comprise, for instance, a plurality of computers that communicate, for instance via a Wireless Local Area Network (WLAN), and perform various functions.  FIG. 8  illustrates the overall architectural layout of an example GST system  800 , which may include the following nodes and their associated peripheral equipment, for example: a subject vehicle  650 ; base station  850 ; and DME  100 . 
         [0041]    The computer associated with the subject vehicle  650  may perform the various data I/O functions within the subject vehicle  650 , and provide the measured data to the rest of the system. Additionally, the subject computer may control discrete events within the subject vehicle  650 . The subject vehicle  650  node may comprise the following components, for example: notebook computer; differential GPS receiver; tri-axial accelerometer; digital I/O board to monitor and control discrete events (e.g., sense ACAT warning on/off, illuminate LEDs, initiate open-loop braking, provide audible alerts); and wireless LAN bridge, for instance. 
         [0042]    The base station  850  may act as the central hub for all communications and allow the operator to monitor and control the system. The base station  850  may comprise the following components, for example: Differential GPS (DGPS) base station receiver; notebook computer; joystick; wireless LAN router; and radio transmitter to provide emergency-stop capability, for instance. 
         [0043]    The computer associated with the base station  850  may allow the system operator to run a complete suite of tests from a single location. From the computer associated with the base station  850 , the operator may perform the following functions, for example: setup and configuration of subject vehicle  650  and GST computers via remote connection; monitor subject vehicle  650  and GST positions, speeds, system health information and other system information; setup of test configuration; test coordination; post-test data analysis; and selection of GST modes, including, for example: hold; manual; semi-autonomous; and fully autonomous, for instance. Additionally, the functions of the computer associated with the base station  850  may also be accomplished on the computer associated with the subject vehicle  650 , reducing the number of computers in the computer network. In this embodiment of a GST, the base station, or operator&#39;s console would be located in the subject vehicle  650   
         [0044]    The DGPS receiver in the base station  850  may provide corrections to the roving DGPS receivers in both the DME  100  and the subject vehicle  650  via a WLAN or other communications network. This may be accomplished without the need for a separate DGPS radio modem, minimizing the number of antennas on each node of the system. This may be important in the case of the DME  100 , since all connections to antennas are typically made frangible, such that they can separate from the DME  100  in the event of a collision with the subject vehicle  650 . 
         [0045]    Example DME  100  subsystems may comprise the following components, among others, for instance: wireless LAN bridge; PC  104  computer; yaw rate sensor; electronic compass; two brushless DC drive motors and amplifiers; a brushless DC steering motor and amplifier; brake system; RF emergency brake system; DGPS receiver; a DME computer such as a PC  104  computer that performs functions such as the following example functions: Guidance, Navigation and Control (GNC) computations; analog and digital data input and output; inputs, including: differential GPS information; electronic compass (heading angle); yaw rate; drive motor speed; steering angle; drive motor amplifier temperature; drive motor winding temperature; and outputs, including: drive motor torque command; steer motor angle command; brake command; system health monitoring; and data collection, for instance. Other or fewer components may be used in various example embodiments. 
         [0046]    Method of GST Operation 
         [0047]    Prior to testing, paired time-space trajectories for the subject vehicle  650  and GST (e.g., a soft body  600 ,  700 , mounted on a DME  100 ) may be generated. These trajectories should be physics-based, and either can be hypothetical or reconstructed real-world crash scenarios. Trajectories can be specified to result in any manner of collision between the subject vehicle  650  and GST, and can include variations in speed and path curvature for both the subject vehicle  650  and GST. The spatial trajectories may be stored in files which also include subject vehicle  650  and GST speeds along their respective paths, and scenario-specific discrete events. These discrete events (e.g., point of brake application) can be used to control the timing of events in the subject vehicle  650  at known points along the subject vehicle  650  path. These can be used to initiate open-loop braking, illuminate LEDs, or provide audible alerts within the subject vehicle  650 , for example. 
         [0048]    In various embodiments a GST system  800  may have, for instance, four different modes of operation: hold; manual; semi-autonomous; and fully-autonomous. The Hold Mode is the “idle” mode for the GST system. In this mode, the output signals to the steering and drive motors may be nullified, but the GUI for the base station  850  may continue to show data from the GST and subject vehicle  650  sensors. Whenever the GST is switched into this mode from one of the “active” modes (e.g., Manual, Semi-Autonomous or Fully Autonomous), data that was collected during the active mode may be transferred wirelessly to the computer associated with the base station  850  for further analysis. 
         [0049]    The Manual Mode may be completely human-controlled via a joystick associated with the base station  850 . In this mode, the operator may have remote control over the speed and steering of the GST. This mode may be useful in pre-positioning the GST or for returning it to base for charging the batteries, routine service, or for shutting down the system. 
         [0050]    The Semi-Autonomous Mode allows the operator of the base station  850  to control the speed of the GST while the path following may be accomplished autonomously. This may be especially useful for pre-positioning the GST before a given test run, since the GST can be driven starting from any point on the test surface, and it will seek and converge on the desired path. The path-following GNC algorithm also may allow for operation in reverse, allowing the operator to drive the GST in reverse along the path for fast repetition of tests. 
         [0051]    The Fully Autonomous Mode may require no further inputs from the base station  850 . In this mode, the subject vehicle  650  may be driven along the subject vehicle  650  path, and the GST computes the speed and steering inputs necessary to move along its own path in coordination with the subject vehicle  650 , as determined by the pre-programmed trajectory pair. In this way, the longitudinal position of the GST may be driven by the longitudinal position of the subject vehicle  650  such that the GST arrives at the pre-determined collision point at the same moment as the subject vehicle  650 , even accommodating errors in the speed of the subject vehicle  650  (relative to the speed in the trajectory file) as it approaches by adjusting its own speed. As an option, the test engineer can enable a sub-mode in which, if the subject vehicle  650  driver or ACAT system begins to react to the impending collision, the GST speed command may be switched to the speed contained in the trajectory file such that it is no longer dependent upon the speed of the subject vehicle  650 . The switch to this sub-mode may be made automatically (mid-run) when the subject vehicle  650  acceleration exceeds a predetermined threshold (e.g., 0.3 g) or when subject vehicle  650  ACAT system activation may be sensed via a discrete input. In this way, the GST passes through the would-be collision point at the speed prescribed in the trajectory file, irrespective of the position or speed of the subject vehicle  650 . 
         [0052]    Testing with the GST 
         [0053]    During test setup, the paired time-space trajectories may be wirelessly loaded into the DME  100  on-board processor from the base station  850 , and the GST may be placed into the fully autonomous mode. As the subject vehicle  650  begins to travel along its path, its position (as measured by differential GPS) may be transmitted wirelessly to the DME  100  processor, which may be programmed to accomplish lateral and longitudinal control to obtain the desired relative closed-loop trajectories. A given test run can culminate in a collision between the subject vehicle  650  and the GST, as shown in  FIG. 6D , in which case, the GST may be brought to a stop using a radio transmitter, separate from the WLAN, which can actuate the onboard brakes of the GST, and disable the drive motors. Test data may be automatically transmitted wirelessly from the DME  100  to the computer associated with the base station  850  once the operator transitions from the Fully Autonomous mode to the Hold mode. The soft car  600  can then be reassembled on the DME  100 , usually within 10 minutes with a crew of two, and the GST can then be repositioned for the next run. 
         [0054]    The GST may employ high-performance and high-efficiency components, allowing it to reach relatively high speeds and achieve high positional accuracy along its trajectory, both laterally and longitudinally. Brushless DC drive motors efficiently deliver high power from a small package, and a Differential GPS receiver provides high positional accuracy. The GNC algorithm is able to utilize the capabilities of these sensors and actuators to maximize the utility of the test methodology. 
         [0055]    Results 
         [0056]    A complete listing of GST performance specifications of example embodiments disclosed herein is shown below in Table 1. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Example GST Performance Specifications 
               
             
          
           
               
                   
                 Specification 
                 Value 
               
               
                   
                   
               
               
                   
                 DGPS positional accuracy 
                 1 cm (depending on DGPS 
               
               
                   
                   
                 receiver) 
               
               
                   
                 DME waypoint accuracy 
                 Lateral: 300 mm 
               
               
                   
                   
                 Longitudinal: 300 mm 
               
               
                   
                 DME top speed (alone) 
                 80 km/h 
               
               
                   
                 DME + Soft Car speed 
                 &gt;55 km/h (demonstrated) 
               
               
                   
                 Maximum closing speed at 
                 110 km/h (demonstrated) 
               
               
                   
                 impact 
               
               
                   
                 Longitudinal acceleration 
                 ±0.3 g 
               
               
                   
                 Longitudinal deceleration 
                 −0.6 g 
               
               
                   
                 under braking 
               
               
                   
                 Lateral acceleration 
                 ±0.3 g 
               
               
                   
                 Distance traveled per battery 
                 4 km at 40 km/h 
               
               
                   
                 charge 
                 (theoretical) 
               
               
                   
                 Remote control range 
                 0.5 km 
               
               
                   
                 Drive motor performance 
                 2 brushless DC drive 
               
               
                   
                   
                 motors, totaling: 
               
               
                   
                   
                 30 kW peak 
               
               
                   
                   
                 6 kW continuous 
               
               
                   
                 Bus voltage 
                 200 VDC 
               
               
                   
                 Turning radius 
                 &lt;3 m 
               
               
                   
                 Visibility with Soft Car 
                 &gt;0.5 km 
               
               
                   
                 body, daylight 
               
               
                   
                 Battery charge time 
                 30-40 min (for full charge 
               
               
                   
                   
                 of depleted batteries) 
               
               
                   
                 Soft Car reassembly time 
                 10 minutes 
               
               
                   
                   
               
             
          
         
       
     
         [0057]    The GST System  800  is a fully-functional and proven system for evaluating ACATs throughout the entire pre-conflict and conflict scenario up to the time of collision. By enabling the ACAT to be evaluated up to the time of collision, the GST System  800  allows the mitigation capabilities of ACATs to be evaluated in a way that cannot be achieved via testing that does not involve actual collisions. Additionally, the DME  100  allows the evaluation of ACATs in conflict scenarios where the CP is not static. The full-sized soft car  600  allows evaluations of the ACAT in any crash configuration without requiring specific soft targets  600  for each configuration (e.g., rear-end soft targets). 
         [0058]    As one example, the GST System  800  was used in the evaluation of a prototype Advanced Collision Mitigation Braking System (A-CMBS). The A-CMBS system was designed to alert the driver in the event of a likely collision and to mitigate the collision severity through automatic application of the brakes for imminent collisions. The test matrix for this evaluation consisted of thirty-three unique crash scenarios, representing four different crash types, repeated with and without the ACAT active. The crash types involved were: Pedestrian; Rear end; Head-on; and Crossing path. During the course of testing, the GST was struck or run over by the subject vehicle  650  more than sixty-five times without being damaged or causing damage to the subject vehicle  650 . 
         [0059]    By repeating the same conflict scenario with and without the ACAT active, the evaluation methodology allows the evaluator to determine both the reduction in number of collisions due to the ACAT and the reduction in collision severity (i.e., closing speed, contact points, relative heading angle) when a collision occurs. Evaluation of the reduction in collision severity can be achieved because the subject vehicle  650  and the GST positions and speeds may be continuously recorded with high precision. Additionally, a more rigorous analysis of the collision severity in a given test can be achieved by determining the predicted collision delta-V (change in velocity) for each test by using a multi-body crash simulation tool. 
         [0060]    As will be apparent to persons skilled in the art, modifications and adaptations to the above-described example embodiments of the invention can be made without departing from the spirit and scope of the invention, which is defined only by the following claims.