1	SMAC 2003 The Automatic Iteration of SMAC McHenry Consultants, Inc. Cary, NC E-mail: info@mchenrysoftware.com Website: www.mchenrysoftware.com
2	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work Research Approach Results Discussion and Conclusions Future Plans
3	SMAC2003 The Automatic Iteration of SMAC What is SMAC?
4	SMAC2003 The Automatic Iteration of SMAC What is SMAC?
5	SMAC2003 The Automatic Iteration of SMAC What is SMAC?
6	SMAC2003 The Automatic Iteration of SMAC What is SMAC?
7	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Reduces or eliminates the need to manually iterate Provides testing and refinement of evidence match. Allows sensitivity testing of input variables Includes unlimited objective iterations
8	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Saves time! Time required for “best match” limited only by processor speed
9	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work Jones, SAE 750894 “To make SMAC ‘user-orientated’ so that users can operate with ease” Found that it is “insufficient to iterate on rest positions alone”
10	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work Moffatt and Byrd, 1980 (DOT-HS-8-01820) Iterated impact speeds, steering & braking Limited by computer costs and capabilities
11	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work CRASH-97 – 1997, (SAE 970949) Used automatic iteration of SMAC for motions between separation and rest to refine separation speeds Did not include collision simulation due to computational time considerations
12	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work Research Approach With advent of gigahertz Pentium machines, iteration of complete SMAC including collision feasible This project an extension of our prior work on CRASH-97 (SAE 970949)
13	Research Approach:
14	Correlation factor function What are important measures in any accident reconstruction? Trajectory measurements Damage measurements
15	Trajectory Measurements Use Measured Scene Evidence
16	SMAC Correlation Function Trajectory measurements The approximate positions and orientations of the vehicles at impact The measured positions and orientations of the vehicles at rest Distance POI to POR for each vehicle Azimuth angle POI to POR for each vehicle Direction of the System Momentum
17	Damage Measurements: Use Vehicle Damage Evidence
18	SMAC Correlation Function Damage measurements: Damage width Damage depth Damage area Centroid of the damage region Clock direction of the approximate PDOF
19	SMAC Correlation Factor Damage
20	ITERATION PROCEDURE Collision responses highly nonlinear Any function minimization technique must handle step discontinuities Restarts to insure a global v local minimum Weighting factors to establish priorities Initially to grossly match evidence Secondarily to assist in refinement of match Auxiliary calculations and checks To help guide the iteration procedure
21	ITERATION PROCEDURE Starting Values for ITERATION Original intent was simply for improvement CRASH-type interface and information CRASH original intent as SMAC preprocessor Information required: Impact positions and headings. Rest positions and headings. Wheel steer and drag Vehicle type and specifications Damage measurements.
22	ITERATION PROCEDURE For Initial development and testing of SMACITER Used SMAC generated reconstructions based on the RICSAC tests Final testing of SMACITER Used ‘raw’ reported test results and other high confidence reconstructions to test convergence ability of SMACITER
23	ITERATION PROCEDURE Variables iterated Initial Speeds and Positions Steering and Braking Minor adjustments of steering and braking within ranges of uncertainty during iteration Sideslip and Angular Velocity Options Provide ability to address control losses preceding impact
24	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work Research Approach Results
25	RICSAC Test#4
26	RICSAC Test#4
27	RICSAC Test#4 1^st Pass with CRASH results: 31.9 MPH
28	RICSAC Test#4 SMACITER
29	RICSAC Test#4 SMACITER Final Results, 38.3 MPH
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31	RICSAC Test#8
32	RICSAC Test#8 Impact Speeds 20.8 MPH, 20.8 MPH
33	RICSAC Test#8, SMAC RUN with CRASH Speeds 19.5 MPH, 24.5 MPH
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41	SMAC 1^st Pass
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43	SMACITER Test with High Confidence Reconstruction
44	SMACITER
45	Final Result
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47	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work Research Approach Results Discussion and Conclusions
48	Discussion and Conclusions
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52	Discussion and Conclusions SMACITER is a tool to aid and assist an accident investigation Feasibility of the automatic iteration of SMAC has been demonstrated This research represents the 1^st validation of SMAC without using Impact Speed as input SMACITER converges towards evidence match Yields impact velocities within ±12% Yields ΔV’s within ±8%
53	Discussion and Conclusions CRASH serves its original purpose as a pre-processor for SMAC A correlation factor or “score” is a desirable means of ranking the achieved match of evidence and thereby the quality and reliability of the reconstruction
54	SMAC2003 The Automatic Iteration of SMAC What is SMAC? Why Automatically Iterate SMAC? Prior Work Research Approach Results Discussion and Conclusions Future Plans
55	FUTURE PLANS Additional refinements of SMACITER Complete comparison of SMACITER with all available full-scale tests Further evaluation of a correlation factor or “score” as a potential measure of reconstruction accuracy Implementation of Restitution enhancements per SAE 970960 3D components – merging of 2 HVOSM vehicles with refined SMAC
56	"End of Presentation" End of Presentation Thank you!