Analysis of Stability
Control Systems for
Tractor-Semitrailers
John Woodrooffe, Dan Blower,
Paul E. Green - UMTRI
Larger NHTSA Study
Safety Benefits of Stability Control Systems for Tractor-­‐Semitrailers •  Daniel Blower •  Timothy Gordon •  Paul E. Green •  Brad Liu •  Peter Sweatman Purpose: Estimate safety benefits of ESC
and RSC for tractor-semitrailers in rollover
and yaw instability crashes"
With Arvin-Meritor, sponsored by NHTSA"
Technologies investigated
•  Full electronic stability control (ESC) on the tractor. •  Tractor-­‐based roll stability control (RSC). •  Trailer-­‐based RSC •  Tractor ESC in conjuncEon with trailer-­‐
based RSC Study Design
Prime Activity Modules"
Fleet Case
Studies"
•  Identify
effectiveness of
systems in fleets"
•  Identify crash types
most affected"
•  Obtain fleet crash
rate reduction
estimates"
•  Obtain fleet cost
effectiveness"
•  Identify crash
scenarios"
LTCCS"
Analysis"
•  Perform
clinical
analysis of PARs
and crash
reconstruction
documents"
•  Confirm / modify
crash scenarios
hypotheses"
National Crash
Databases"
•  Determine
frequency of
selected crash
scenarios"
•  Determine
severity
characteristics of
selected crash
scenarios "
•  Estimate likely
benefits"
Naturalistic Driving
Databases"
•  Provide insight
into probable
incident approach
speed range"
Hardware"
in-the-Loop"
•  Examine
the
detailed sequence
of various crash
scenarios"
•  Estimate speed
ranges where
technologies can
be effective for
various driving
conditions"
•  Study the relative
performance of the
various
technologies"
Crash Data Analysis
Rollover and Loss of Control"
•  Five Years Of GES Data (2000 –
2004)"
•  Five Years Of TIFA Data (2000 –
2004)"
•  GES Nonfatal, TIFA Fatal"
•  Nationally Representative
Databases"
•  Results For Tractor Semitrailers"
Large Truck Crash Causation
Study Cases"
LTCCS provides detailed information about
crash events:"
–  Scene diagram"
–  Detailed narrative"
–  Detailed coded crash events (matches GES;
can be approximated in TIFA)"
–  Matches TIFA on detail of physical
configuration of the vehicle (weights, lengths,
axle count, cargo weight and type, etc.)"
Review of LTCCS Yaw & Roll
Instability Crashes"
•  Review of:"
–  83 yaw instability cases "
–  81 roll instability cases"
•  Assess for"
–  Accuracy of coding"
–  Crash details (radius of curvature, curve entry
speed)"
–  Relevance of roll & yaw control technologies
(likely, probably, unlikely, unknown)"
LTCCS Rollover Case for Simulation
• Road curved
• Dry surface
• Cargo: loaded
3-axle tractor
pulling bottom
dump.
14,000 kg cargo
(dirt)
28,000 kg gross
weight
Est. 65 km/h
Simulating Rollovers in Curves
Distribution of Lateral Acceleration Peak Ay
FOT Data Consist of 3,460 Passes Through 42 Curves
(naturalistic)"
Distribu(on of Rollovers On Curve by Curve Radius and Roll Posi(on Radius"
Within 100m of"
curve start"
Past 100m
of curve
start"
Total"
<100m"
23"
20"
43"
>100m"
7"
21"
28"
Of rollovers, 20/43 entered curve below Vc (radius < 100m)"
Of rollovers, 21/28 entered curve below Vc (radius > 100m)"
Use this information to shift distributions to the right"
Distribution of Peak Ay Converted to km/h
for Two Curve Radii
68m curve radius
227m curve radius
Km/h
Km/h
Schematic Trajectory of Maneuver
(Transient to Constant Curve)
Spiral transiEon rate of 1.3 m/s3 is based on the AASHTO prescribed curve entry geometry corresponding to a steady-­‐state lateral acceleraEon of 1.5 m/s2. Hardware in the loop
SimulaEon •  TruckSim offers Real-­‐Eme SimulaEon in CombinaEon with SIMULINK and the TruckSim Animator Hardware in-the-Loop
Hardware •  Uses all pneumaEc and electronic control elements (except the air compressor and drier,) •  Power unit components consistent with 3-­‐axle power unit and 2-­‐axle semi trailer to be used for HiL validaEon •  The enEre pneumaEc system from air reservoirs, through treadle and other system valves to brake actuaEon chambers will be set up in the UMTRI laboratory •  Appropriate fiZngs and proper length tubing and hose will be used •  The brake chambers will be installed on real S-­‐cam brakes such that they have appropriate pressure/deflecEon properEes. Vehicle speed time history for ABS, RSC and
ESC technologies
Fitting the technologies to all tractor
semitrailers"
EsEmated RSC benefits EsEmated ESC benefits •  3,489 crashes, 106
fatalities, and 4,384
injuries "
•  $1.456U.S. billion/yr "
•  4,659 crashes, 126
fatalities, and 5,909
injuries "
•  $1.738U.S. billion/yr Conclusions
•  Electronic stability systems were found to provide substanEal safety benefits •  Because ESC addresses both rollover and yaw crashes and it miEgates more rollover crashes (through addiEonal braking capabiliEes over RSC), the expected benefit for ESC systems is greater than for RSC. Conclusions
•  The analysis found that ESC provided more overall safety benefit than RSC. The difference between the esEmated effecEveness of RSC and ESC varied among crash scenarios. •  Relying on the general LOC or rollover categories captures a wide range of crashes, many of which have no relevance to the technology. Conclusions
•  The benefit esEmates are limited to five-­‐axle tractor-­‐semitrailers operaEng within the U.S. •  The study was not able to assess benefits a\ributable to less obvious crash types that may nevertheless have an unforeseen connecEon to the technology.