Crash Data Presentation Texas Association of Accident Reconstruction
Specialists Conference
2014
Consortium Website
All data from crash testing and this presentation will be available at
http://tucrrc.utulsa.edu
Credentials
User: TUCRRCmember Password: TUCRRCpassword
TAARS 2014 http://tucrrc.utulsa.edu 2
Running into Trailers
Common theme for crash testing
IPTM 2004
IPTM 2012
IATAI 2013
Tennessee 2014
TAARS 2014
Common occurrence on highways and interstates.
TAARS 2014 http://tucrrc.utulsa.edu 3
Order of Presentation
Crash Test Videos
Crash Testing Setup and Instrumentation
Rotational Mechanics Analysis
Restitution Analysis
Aggregated Crash Test Analysis
TAARS 2014 http://tucrrc.utulsa.edu 4
Tennessee 2014
TAARS 2014 http://tucrrc.utulsa.edu 5
Tennessee 2014
TAARS 2014 http://tucrrc.utulsa.edu 6
IPTM Special Problems
TAARS 2014 http://tucrrc.utulsa.edu 7
IPTM Special Project
TAARS 2014 http://tucrrc.utulsa.edu 8
TAARS 2014
Open Quicktime to watch videos
TAARS 2014 http://tucrrc.utulsa.edu 9
TAARS 2014 Summary
Crash 1
2005 Chrysler Sebring
Weight: 3395
Impact Speed
Vbox 3i: 46.11
Video Vbox: 45.66 mph
eGPS-200: 45.86
Crash 2
2004 Mercury Sable
Weight: 3043 lb
Impact Speed
Vbox 3i: 45.98
Rear Dual Displacement 13.5 ft
Angle of trailer rotation: ~24.5 deg
TAARS 2014 http://tucrrc.utulsa.edu 10
DATA ACQUISITION SYSTEMS AND SETUP
TAARS 2014 http://tucrrc.utulsa.edu 11
Racelogic VBox 3i
100Hz GPS system
Serial (CAN) communication
Compact flash logging
Brake trigger
Inertial Measurement Unit
Tri-axial accelerometer
Tri-axial gyroscope
TAARS 2014 http://tucrrc.utulsa.edu 12
Racelogic Video VBox
10Hz/20Hz GPS system
4 Cameras
Microphone
Compact flash logging
TAARS 2014 http://tucrrc.utulsa.edu 13
eDAQ Data Acquisition
Rugged system designed for use in harsh environments
Enables simultaneous and synchronous recording of multiple channels with different types of instruments
Convenient data recording modes
Proprietary interface
Infield Software http://www.hbm.com/en/menu/support/software-firmware-downloads/data-acquisition-systems/somat/#c33997
TAARS 2014 http://tucrrc.utulsa.edu 14
eDAQ
TAARS 2014 http://tucrrc.utulsa.edu 15
4 Layers
DIO
Digital I/O
HLS
High level analog
ECOM
Vehicle network communications
Instruments
TAARS 2014 http://tucrrc.utulsa.edu 16
eGPS-200Plus Combines data from 2 GPS antennas and IMU to
provide several kinematic measurements at 200Hz
Measurements Acceleration (All 3 axis)
Angular velocity (All 3 Axis)
Speed
Heading, altitude, longitude
Slip angle
Instruments
Gyroscope Tri-axial measurements
±600 deg/s rates
400 Hz bandwidth
TAARS 2014 http://tucrrc.utulsa.edu 17
Accelerometer Tri-axial measurements
±250gs
5,000 Hz bandwidth
eDAQ Data Recording Modes
Time history
Records continuously
Burst history
Buffer data
Records data in a
predefined interval
Simplifies data
processing
TAARS 2014 http://tucrrc.utulsa.edu 18
Interface (Web)
TAARS 2014 http://tucrrc.utulsa.edu 19
Limited access
Manage networked cameras
Quick test startup
VC4000DAQ
TAARS 2014 http://tucrrc.utulsa.edu 20
10Hz GPS
Brake pedal sensor
Tri-axial accelerometer
Used to determine drag coefficient
Attaching Accelerometer
TAARS 2014 http://tucrrc.utulsa.edu 21
SAE Sign Convention
MATAI 2014 http://tucrrc.utulsa.edu 22
INLINE IMPACT CHRYSLER SEBRING INTO TRAILER
Crash Test 1 Data
TAARS 2014 http://tucrrc.utulsa.edu 23
System Momentum
System Momentum In + External Impulse = System Momentum Out
Planar components: X, Y, and q.
A system is defined as something you can define a boundary with.
Consistent boundary (Eularian system)
Consistent Objects (Lagrangian system)
Forces act on boundaries.
TAARS 2014 http://tucrrc.utulsa.edu 24
Inline system
System defined as the two vehicles where the interaction boundary is the road surface.
External impulses occur at the boundary.
Don’t need to include collision forces
Can also define the boundaries around each vehicle.
Need to include both collision forces and road forces.
TAARS 2014 http://tucrrc.utulsa.edu 25
Foundations
Work and Energy: Kinetic Energy In = Damage Energy + Kinetic
Energy Out
Impulse and Momentum Momentum In + External Impulse = Momentum Out
External Impulse can be from collision forces and friction
Kinematics Speed in + Delta V = Speed Out
Restitution = (V1,in – V2,in)/(V2,out – V1,out)
TAARS 2014 http://tucrrc.utulsa.edu 26
DATA FROM INSTRUMENTS
Inline Crash
TAARS 2014 http://tucrrc.utulsa.edu 27
Vbox 3i Data
TAARS 2014 http://tucrrc.utulsa.edu 28
eDAQ Synchronized Data
TAARS 2014 http://tucrrc.utulsa.edu 29
eDAQlite_Data_Crash1_TX2014.sif - eGPS@speed_3d.RN_1
spee
d_3d
(km
/h)
01020304050607080
eDAQlite_Data_Crash1_TX2014.sif - [email protected]_1
VB
Vel
ocity
(kno
ts)
0
10
20
30
40
50
eDAQlite_Data_Crash1_TX2014.sif - IMU@accel_x_05.RN_1
Time(secs)
90 92 94 96 98 100 102
acce
l_x_
05(g
)
-120-100-80-60-40-200
2040
Impact Speeds
TAARS 2014 http://tucrrc.utulsa.edu 30
eDAQlite_Data_Crash1_TX2014.sif - eGPS@speed_3d.RN_1
spee
d_3d
(km
/h)
01020304050607080
eDAQlite_Data_Crash1_TX2014.sif - [email protected]_1
VB
Vel
ocity
(kno
ts)
0
10
20
30
40
50
eDAQlite_Data_Crash1_TX2014.sif - IMU@accel_x_05.RN_1
Time(secs)
101.0 101.2 101.4 101.6 101.8
acce
l_x_
05(g
)
-120-100-80-60-40-200
2040
x:101.185 y:73.8 n:4942
x:101.18 y:40.17 n:2470
x:101.1842 y:0.257583 n:198546
45.86 mph
46.22 mph
Crash Pulse from Chrysler
TAARS 2014 http://tucrrc.utulsa.edu 31
eDAQlite_Data_Crash1_TX2014.sif - IMU@accel_x_05.RN_1
Time(secs)
101.20 101.25 101.30 101.35 101.40 101.45
acce
l_x_
05(g
)
-120
-100
-80
-60
-40
-20
0
20
40x:101.185 y:0.322577 n:198550 x:101.3286 y:0.0347443 dx:0.1436 dy:-0.287833
Chrysler Delta V in X
TAARS 2014 http://tucrrc.utulsa.edu 32
Calculator_00220.sif - Computed from X Accelerometer
Time(secs)
101.1 101.2 101.3 101.4 101.5 101.6
Del
ta V
(mph
)
-50
-40
-30
-20
-10
0
10x:101.186 y:-0.0167915 n:256 x:101.3254 y:-49.5999 dx:0.1394 dy:-49.5831
Delta V = -49.6 mph
Delta T = 139 msec
Separation after impact
TAARS 2014 http://tucrrc.utulsa.edu 33
Relative Accelerations
TAARS 2014 http://tucrrc.utulsa.edu 34
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_X_06.RN_1
Acc
el_X
_06(
g)
-200-150-100-500
50100150
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_X_43.RN_1
Acc
el_X
_43(
g)
-8-6-4-202468
10
eDAQ_Data_crash1_TX2014.sie - GPS@accel_x.RN_1
Time(secs)
402.0 402.5 403.0 403.5 404.0 404.5
acce
l_x(
G)
-3-2-101234
Near Impact
Middle of Trailer
Tractor Platform
Same Scale (X Direction)
TAARS 2014 http://tucrrc.utulsa.edu 35
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_X_06.RN_1
Acc
el_X
_06(
g)
-40
-20
0
20
40
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_X_43.RN_1
Acc
el_X
_43(
g)
-40
-20
0
20
40
eDAQ_Data_crash1_TX2014.sie - GPS@accel_x.RN_1
Time(secs)
402.4 402.6 402.8 403.0 403.2 403.4 403.6 403.8
acce
l_x(
G)
-40
-20
0
20
40
Y Axis Accelerations
TAARS 2014 http://tucrrc.utulsa.edu 36
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_Y_06.RN_1
Time(secs)
402.4 402.6 402.8 403.0 403.2 403.4 403.6
Acc
el_Y
_06(
g)
-36
-12
12
36
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_Y_43.RN_1
eDAQ_Data_crash1_TX2014.sie - GPS@accel_y.RN_1
Z- Axis Accelerations
TAARS 2014 http://tucrrc.utulsa.edu 37
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_Z_06.RN_1
Time(secs)
402.5 403.0 403.5 404.0
Acc
el_Z
_06(
g)
-40
-20
0
20
40
eDAQ_Data_crash1_TX2014.sie - IMU_data@Accel_Z_43.RN_1
eDAQ_Data_crash1_TX2014.sie - GPS@accel_z.RN_1
Delta-V in X from all Accels
TAARS 2014 http://tucrrc.utulsa.edu 38
Rear X Accel.
Time(secs)
402.0 402.5 403.0 403.5 404.0 404.5 405.0 405.5
Del
ta V
(mph
)
-3
-2
-1
0
1
2
3
4
5
Middle X Accel.
Tractor Accel (e-GPS)
x:402.3874 y:0.010843 n:441
x:402.3874 y:0.00528648 n:616
x:402.385 y:0.008784 n:72
x:402.5234 y:4.31572 dx:0.136 dy:4.30488
x:402.5234 y:4.30905 dx:0.136 dy:4.30377
x:402.525 y:4.09444 dx:0.14 dy:4.08566
Zoomed in on Delta-V (4.3 mph in 115 msec)
TAARS 2014 http://tucrrc.utulsa.edu 39
Rear X Accel.
Time(secs)
402.30 402.35 402.40 402.45 402.50 402.55 402.60 402.65
Del
ta V
(mph
)
-1
0
1
2
3
4
5
Middle X Accel.
Tractor Accel (e-GPS)
x:402.4026 y:0.0406617 n:517
x:402.4026 y:-0.000231389 n:692
x:402.405 y:-0.001098 n:76
x:402.5176 y:4.29468 dx:0.115 dy:4.25402
x:402.5176 y:4.36877 dx:0.115 dy:4.369
x:402.52 y:4.15373 dx:0.115 dy:4.15483
Observations
Rigid body assumption:
Common delta-V values for the whole rig
Common times
Confidence of measurements
Acceleration data shows shock attenuation
150 g’s near impact
4 g’s at cab
eGPS accelerometer has too much damping (not great for shock events)
TAARS 2014 http://tucrrc.utulsa.edu 40
Restitution
Impact speed of car: 46 mph
Delta V of Car: 49.6 mph
Post impact Speed of car: -3.6 mph (~0)
Impact Speed of Trailer: 0 mph
Post Impact Speed (Delta V) of Trailer: 4.3 mph
𝑒 =𝑉1,𝑜𝑢𝑡−𝑉2,𝑜𝑢𝑡
𝑉2,𝑖𝑛−𝑉1,𝑖𝑛=−3.6−4.3
0−46= 0.172
TAARS 2014 http://tucrrc.utulsa.edu 41
Reconstruction Strategy
Assume known speed of tractor-trailer
If not an underride: Calculate Delta V from Crush
Assume restitution of 0.1-0.2 for impact speed
If underride: Look for EDR data…
Crush analysis doesn’t account for some energies.
50% low estimate on impact speed for Chrysler in this case.
Closing speeds are almost always low.
TAARS 2014 http://tucrrc.utulsa.edu 42
SABLE INTO TRAILER DUALS AT 90 DEGREES
TAARS 2014 Crash #2:
TAARS 2014 http://tucrrc.utulsa.edu 43
Crash 2 Video
TAARS 2014 http://tucrrc.utulsa.edu 44
Fundamentals of Crash Reconstruction
Chapter 9: Rotational Mechanics
TAARS 2014 http://tucrrc.utulsa.edu 45
Tractor Trailer Axle Data
Weights
TAARS 2014 http://tucrrc.utulsa.edu 46
Tractor Trailer Weights (lb)
Left Front Right
4820 |- -| 4480
2900 |- -| 3320
2320 |- -| 2180
2040 |- -| 1750
2300 |- -| 2300
Axle Weights (lb)
Left Front Right
4820 |- Steer -| 4480
2900 |- Drive 1 -| 3320
2320 |- Drive 2 -| 2180
2040 |- Trailer 1 -| 1750
2300 |- Trailer 2 -| 2300
Total: 28,410 lb
Portable Scales
Weights from Wrecker
Box Van Landing gear: 4640 lb
Box Van Rear Axles: 7800 lb
Volvo Steer Axle: 8200 lb
Volvo Drive Axles: 7240 lb
Total Combined Weight: 27,880 lb Compared to 28,410 lb from other scales (2%
difference)
Mercury Sable: 2968 + 75 = 3043 lb
Chrysler Sebring: 3320 + 75 = 3395 lb
TAARS 2014 http://tucrrc.utulsa.edu 47
Mercury Impact Speed ~46 mph (Crash 2)
TAARS 2014 http://tucrrc.utulsa.edu 48
Delta V: ~38 mph
TAARS 2014 http://tucrrc.utulsa.edu 49
Rear Dual Displacement
TAARS 2014 http://tucrrc.utulsa.edu 50
Angle of Rotation
TAARS 2014 http://tucrrc.utulsa.edu 51
24.6 Deg
What About Trailer Rotation?
Assume the Trailer is a Rigid Body rotating around the king pin
Tractor did move a little
Trailer had rolling motion
Angular quantities are the same everywhere
Acceleration of Rigid Body 𝑎 𝑃 = 𝑎 𝑂 + 𝛼 × 𝑟 𝑃/𝑂 + 𝜔 × (𝜔 × 𝑟 𝑃/𝑂)
Y direction accel. depends on lever arm
TAARS 2014 http://tucrrc.utulsa.edu 52
𝜔 × (𝜔 × 𝑟 𝑃/𝑂)
Graphic of Rotation
TAARS 2014 http://tucrrc.utulsa.edu 53
x
y
+q 𝑟
𝛼 × 𝑟 𝑃/𝑂
Y Axis Accelerations
TAARS 2014 http://tucrrc.utulsa.edu 54
eDAQ_Data_crash2_TX2014.sie - IMU_data@Accel_Y_06.RN_1
Time(secs)
784.0 784.5 785.0
Acc
el_Y
_06(
g)
-150
-100
-50
0
50
100
150
eDAQ_Data_crash2_TX2014.sie - IMU_data@Accel_Y_43.RN_1
eDAQ_Data_crash2_TX2014.sie - GPS@accel_y.RN_1
Note: Middle Accelerometer
(blue) was mounted with z axis
up and y axis out driver’s side
(opposite SAE).
Zoomed on Y Accelerations
TAARS 2014 http://tucrrc.utulsa.edu 55
Rear Trailler Accelerometer (Y)
Time(secs)
783.70 783.75 783.80 783.85 783.90 783.95 784.00
Acc
eler
atio
n (g
)
-100
-67
-33
0
33
67
100
Middle Accelerometer (Y)
Tractor Accelerometer (Y)
Delta V in Y for Tractor
TAARS 2014 http://tucrrc.utulsa.edu 56
Tractor Accelerometer in Y
Time(secs)
782 784 786 788 790 792 794
Del
ta V
(m
ph)
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0x:793.056 y:No Data n:No Data
Delta V in Y for Trailer Middle
TAARS 2014 http://tucrrc.utulsa.edu 57
Calculator_00248.sif - Calculated from Middle Y Accel
Time(secs)
783 784 785 786 787 788 789 790
Del
ta V
(mph
)
-10
-8
-6
-4
-2
0
2
Delta V in Y near Impact
TAARS 2014 http://tucrrc.utulsa.edu 58
Calculated from Y Accel near impact
Time(secs)
783.5 784.0 784.5 785.0 785.5 786.0 786.5 787.0 787.5
Del
ta V
(m
ph)
-20
-15
-10
-5
0
5
Delta V Comparison
TAARS 2014 http://tucrrc.utulsa.edu 59
Calculator_00239.sif - Tractor Y Accel
Time(secs)
784.0 784.5 785.0 785.5 786.0
Del
ta V
(m
ph)
-20
-15
-10
-5
0
5
Calculator_00247.sif - Impact Y Accel
Calculator_00248.sif - Middle Y Accel
Trailer Crash Pulse
TAARS 2014 http://tucrrc.utulsa.edu 60
Calculator_00239.sif - Tractor Y Accel
Time(secs)
783.70 783.75 783.80 783.85 783.90
Del
ta V
(m
ph)
-20
-15
-10
-5
0
5
Calculator_00247.sif - Impact Y Accel
Calculator_00248.sif - Middle Y Accel
x:783.7 y:-0.000373315 n:32
x:783.699 y:-0.106395 n:648
x:783.699 y:-0.020098 n:555
x:783.79 y:0.206446 dx:0.09 dy:0.206819
x:783.7876 y:-17.6722 dx:0.0886 dy:-17.5658
x:783.7876 y:-8.25392 dx:0.0886 dy:-8.23382
88 ms
-8.23 mph
-17.55 mph
Yaw and Roll Rate of Trailer
TAARS 2014 http://tucrrc.utulsa.edu 61
eDAQ_Data_crash2_TX2014.sie - IMU_data@Yaw_48.RN_1
Yaw
_48(
deg/
sec)
-150-100-500
50100150200
eDAQ_Data_crash2_TX2014.sie - IMU_data@Roll_48.RN_1
Rol
l_48
(deg
/sec
)
-150-100-500
50100150200250
eDAQ_Data_crash2_TX2014.sie - IMU_data@Accel_Y_43.RN_1
Time(secs)
784.0 784.5 785.0 785.5 786.0 786.5
Acc
el_Y
_43(
g)
-30
-20
-10
0
10
20
30
Trailer to Truck Yaw Rate Comparison
TAARS 2014 http://tucrrc.utulsa.edu 62
eDAQ_Data_crash2_TX2014.sie - IMU_data@Yaw_48.RN_1
Time(secs)
784.0 784.5 785.0 785.5 786.0
Yaw
_48(
deg/
sec)
-150
-100
-50
0
50
100
150
200eDAQ_Data_crash2_TX2014.sie - GPS@yaw_rate.RN_1
Yaw and Roll Rate
TAARS 2014 http://tucrrc.utulsa.edu 63
eDAQ_Data_crash2_TX2014.sie - IMU_data@Roll_48.RN_1
Time(secs)
784.0 784.5 785.0 785.5 786.0 786.5 787.0
Rol
l_48
(deg
/sec
)
-150
-100
-50
0
50
100
150
200
250eDAQ_Data_crash2_TX2014.sie - IMU_data@Yaw_48.RN_1
Restitution
TAARS 2014 http://tucrrc.utulsa.edu 64
Yaw and Roll Angle
TAARS 2014 http://tucrrc.utulsa.edu 65
Calculator_00251.sif - Yaw Angle
Time(secs)
783.0 783.5 784.0 784.5 785.0 785.5 786.0 786.5 787.0 787.5
Ang
le(d
eg)
-15
-10
-5
0
5
10
15
20
25Calculator_00252.sif - Roll Angle
Estimate Initial average Angular Velocity
TAARS 2014 http://tucrrc.utulsa.edu 66
Calculator_00251.sif - Yaw Angle
Time(secs)
784.0 784.5 785.0 785.5
Ang
le(d
eg)
-15
-10
-5
0
5
10
15
20
25Calculator_00252.sif - Roll Angle
x:783.7794 y:2.19715 n:1254
x:783.7794 y:3.67005 n:1579
x:783.8794 y:5.98207 dx:0.1 dy:3.78492
x:783.8794 y:6.14531 dx:0.1 dy:2.47526
Slope = 37.84 deg/s
Mercury Speed
TAARS 2014 http://tucrrc.utulsa.edu 67
Restitution Estimation
Mercury Impact Speed: 46 mph
Mercury Post Impact Speed: ~8 mph
Post Impact Point Velocity: ~16 mph
𝑒 =𝑉1,𝑜𝑢𝑡 − 𝑉2,𝑜𝑢𝑡𝑉2,𝑖𝑛 − 𝑉1,𝑖𝑛
≈8 − 16
0 − 46= 0.17
TAARS 2014 http://tucrrc.utulsa.edu 68
Inertial Properties of Trailer
http://deepblue.lib.umich.edu/handle/2027.42/118
Moment of Inertia
945,019 in-lb-sec2
TAARS 2014 http://tucrrc.utulsa.edu 69
Page 148
Actual Crash Weight: 12,440 lb
TAARS 2014 http://tucrrc.utulsa.edu 70
Center of Mass Location
TAARS 2014 http://tucrrc.utulsa.edu 71
TAARS 2014 http://tucrrc.utulsa.edu 72
TENNESSEE CONFERENCE 2014
Comparison to other Crashes
TAARS 2014 http://tucrrc.utulsa.edu 73
Tennessee 2014
TAARS 2014 http://tucrrc.utulsa.edu 74
Tennessee 2014
TAARS 2014 http://tucrrc.utulsa.edu 75
Mapping data
TAARS 2014 http://tucrrc.utulsa.edu 76
EDR DATA FROM UNDERRIDES
TAARS 2014 http://tucrrc.utulsa.edu 77
GMC Envoy Crash Video
TAARS 2014 http://tucrrc.utulsa.edu 78
No Air Bag Deployment
TAARS 2014 http://tucrrc.utulsa.edu 79
Photo of Non-deployment
TAARS 2014 http://tucrrc.utulsa.edu 80
Photo of Non-deployment
TAARS 2014 http://tucrrc.utulsa.edu 81
GMC Envoy Pre-Crash Data
TAARS 2014 http://tucrrc.utulsa.edu 82
GMC Envoy ABS and Δv Crash Data
TAARS 2014 http://tucrrc.utulsa.edu 83
GMC Envoy EDR Δv
TAARS 2014 http://tucrrc.utulsa.edu 84
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 100 200 300 400
Δv (
mph)
Time (ms)
GMC Envoy Δv vs. Time CDR
Accuracy of EDR Data
TAARS 2014 http://tucrrc.utulsa.edu 85
To test accuracy of EDR Data a reference accelerometer was mounted behind the passenger seat of the crash vehicle
GMC Envoy Crash Acceleration Impulse
TAARS 2014 http://tucrrc.utulsa.edu 86
-100
-80
-60
-40
-20
0
20
40
60
80
0 50 100 150 200 250
Acc
ele
ration (
g)
Time (ms)
Crash Impulse Acceleration Accelerometer
GMC Envoy Δv comparison
TAARS 2014 http://tucrrc.utulsa.edu 87
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 50 100 150 200 250 300 350 400
Δv (
mph)
Time (ms)
GMC Envoy Δv vs. Time Accelerometer CDR
Maximum
recorded
velocity
change
Chevy S10 Δv comparison
TAARS 2014 http://tucrrc.utulsa.edu 88
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 50 100 150 200 250
Δv (
mph)
Time (ms)
Chevy S10 Δv vs. Time Accelerometer CDR
Accuracy of EDR Data
Based on the data provided by the reference accelerometer, the EDR Δv is accurate
Similar shape in Δv vs. time graphs validate EDR data
Trend line can be used to extrapolate data past the 150ms memory threshold
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When do air bags deploy?
At the onset of an event, the ACM detects acceleration sufficient to wakeup the crash sensing / decision making algorithm
Based on an evaluation of the sensed acceleration, potentially along information from auxiliary sensors, the ACM makes a decision to Deploy or Not Deploy the supplemental restraints
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Predictive Decision Making
The ACM decision is anticipatory based on pre-programmed criteria
“Jerk” and other criteria are evaluated as long as the crash sensing algorithm is awake
It does not / can not wait for some minimum delta-v threshold to be met
Deployment decision has to be made early to allow time for airbag inflation
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Ideal Airbag Deployment Timing
It is generally held the ideal decision window is ~15-50ms to allow for airbag inflation before occupant contact
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Deployment Timing Example
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Deployment Timing Example
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Deployment Timing Example
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Less than ideal timeline
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When air bags may not deploy
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THP 2014 - Crash #1
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THP 2014 - Crash #1
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THP 2014 - Crash #1
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Leica ScanStation Data
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THP 2014 - Crash #1
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THP 2014 - Crash #1
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THP 2014 - Crash #1
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THP 2014 - Crash #1
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Deployment Timing Example
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THP 2014 - Crash #2
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THP 2014 - Crash #2
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THP 2014 - Crash #2
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THP 2014 - Crash #2
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THP 2014 - Crash #2
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THP 2014 - Crash #2
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Chevy S10 Crash Video
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Displacement Angle
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King-pin
Rear axle
37.6
θ
7.8
𝜃 = 𝑡𝑎𝑛−17.8
37.6= 0.204 𝑟𝑎𝑑 = 11.72°
(Top View)
7.8
37.6
θ
Chevy S10 Pre-Crash Data
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Chevy S10 ABS and Δv Crash Data
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Chevy S10 EDR Δv
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-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 20 40 60 80 100 120
Δv (
mph)
Time (ms)
Chevy S10 Δv vs. Time CDR
Combined EDR Δv
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-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 50 100 150 200 250 300 350 400
Δv (
mph)
Time (ms)
Chevy S10 and GMC Envoy Δv vs. Time
GMC Envoy Chevy S10
Jerk Defined
In physics:
also known as jolt, surge, or lurch
Jerk = the rate of change of acceleration
the derivative of acceleration with respect to time
the second derivative of velocity
the third derivative of position.
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Jerk – Related to Airbag Deployment Decision Making
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DETROIT DIESEL ECM DATA AND NETWORK TRAFFIC
Jeremy Daily on
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DDEC Reports
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Graph Data
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Table Data
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Detroit Diesel Diagnostic Link DDDL
Compare ECM Time Clock
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Speed Record Comparison
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Remarks
Impulse and Momentum data is insufficient to calculate speeds
DeltaV from hvEDR data is not resolved well
Vehicle Network speed has more samples, thus making it a candidate for data, if available.
hvEDR follows the J1587 Road Speed Data.
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ROTATIONAL MECHANICS ANALYSIS FOR RIGHT ANGLE IMPACT
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S-10 Crash Analysis
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• Location of Center of Mass of Trailer • Mass Moment of Inertia of Trailer • Lateral Displacement of Trailer
(Displacement Angle) • Angular Velocity of Trailer • Calculating S-10 delta-V • Calculating pre-impact velocity of S-10 • Accuracy of Calculations vs.
Equipment Data
Determining the location of Center of Mass (C.M.) using Static Analysis
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WRA1 WRA2 WLG
W Location Left Right
LG Landing Gear 3800 4400
RA1 Rear Axle 2600 1800
RA2 Front Axle 2200 1900
Total Trailer Weight (Wtotal) =
16,700 lb.
WTOTAL
Determining the location of Center of Mass (C.M.) using Static Analysis
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Determining the location of Center of Mass (C.M.) using Static Analysis
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50.3 ft.
9.6
13.6
38
47.2
d1
d2
d3
d4
Determining the location of Center of Mass (C.M.) using Static Analysis
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WRA1 WRA2 WLG
WTOTAL O x
y
𝑀𝑂 = 0
x
d1
d2
d3
𝑊𝑅𝐴1(𝑑1) +𝑊𝑅𝐴2(𝑑2) −𝑊𝑇𝑂𝑇𝐴𝐿(𝑋) +𝑊𝐿𝐺(𝑑3) = 0
Determining the location of Center of Mass (C.M.) using Static Analysis
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WRA1 WRA2 WLG
WTOTAL O x
y
x
d1
d2
d3
𝑋 =𝑊𝑅𝐴1(𝑑1) +𝑊𝑅𝐴2(𝑑2) +𝑊𝐿𝐺(𝑑3)
𝑊𝑇𝑂𝑇𝐴𝐿
Location of C.M.
from the rear of the
trailer.
Determining the location of Center of Mass (C.M.) using Static Analysis
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WRA1 WRA2 WLG
WTOTAL O x
y
24.5
d1
d2
d3
𝑋 = 24.5 𝑓𝑡 Location of C.M.
from the rear of the
trailer.
Displacement Angle
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37.6
θ
7.8
7.75ft
Rotational Mechanics- Mass Moment of Inertia
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• Def: Measure of a body’s
resistance to rotational
acceleration about a
specified axis of rotation.
• Depends on geometry and
location of axis of rotation.
• If axis of rotation is NOT
through center of mass,
then Parallel Axis Theorem
must be used.
Rotational Mechanics- Mass Moment of Inertia (Yaw)
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𝐼𝑧 =1
12𝑚(𝑏2 + 𝐿2)
m…mass
b…width of trailer
L…length of trailer
Units: lb-ft-s2 , slug-ft2
𝐼𝑧,𝐶𝑀 =1
12(16700
32.2)(8.52 + 50.32)
𝐼𝑧,𝐶𝑀 = 112,471.73 𝑙𝑏 ∙ 𝑓𝑡 ∙ 𝑠2
Rotational Mechanics- Parallel Axis Theorem
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King-pin
d=22.6
𝐼𝑧,𝐾𝑃 = 𝐼𝑧,𝐾𝑃 +𝑚𝑑2
𝐼𝑧,𝐾𝑃 = 112,471.73 + (16700
32.2)(22.62)
𝐼𝑧,𝐾𝑃 = 378,308.8 𝑙𝑏 ∙ 𝑓𝑡 ∙ 𝑠2
Rotational Mechanics- Angular Velocity
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King-pin
PDOF
(Center of Axle
Assy.)
h = 35.3
Assumptions:
-50/50 Left/Right Weight Distribution
-Fully rigid king-pin
-Estimate drag-factor (f)
𝜔 = 2𝑤𝑓ℎ𝜃
𝐼𝑧,𝑘𝑝 (eq. 9.67)
f…estimated drag factor (0.6-0.7)
w…weight
h…KP to LOI θ…displacement angle I…mass moment of inertia about the King-pin
Rotational Mechanics- Angular Velocity
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King-pin
PDOF
(Center of Axle
Assy.)
h = 35.3
𝜔 = 2(0.7)(16700)(35.3)(0.204)
378308.8
𝜔 = 0.534857 rad/sec
𝜔
Plug in numbers…
Delta-V of S-10
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King-pin
PDOF
(Center of Axle
Assy.)
h = 35.3
∆𝑣 =𝐼𝑧,𝑘𝑝𝜔
𝑚ℎ
∆𝑣 =(378,308.8)(0.535)
(343032.2)(35.3)
∆𝑣 = 53.9𝑓𝑡
𝑠= 36.7 𝑚𝑝ℎ
(eq. 9.60)
Pre-Impact Velocity of S-10 (v1)
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𝑣1 =𝑣4 + ∆𝑣
1 + 𝑒
𝑣4 = ℎ𝜔
𝑣1 =35.3 0.535 + 53.9
1 + 0
(eq. 9.72)
…linear post-impact velocity of trailer
𝑣1 = 72.7 𝑓𝑡/ sec = 49.62 𝑚𝑝ℎ
𝑣1 𝑣4
𝑒 …Coefficient of restitution (typically 0 - 0.15).
Ratio of speeds after and before impact. 1 –
elastic & 0 – perfectly inelastic.
Calculations vs. Instrument Data
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Calculated Radar eGPS-200 VBOX 3i VVBOX Lite
49.62 48.7 48.72 49.04 48.75
f v1
0.6 45.94
0.65 47.81
0.7 49.62
Calculated Instruments
[mph]
This demonstrates that the principles based on Newtonian
physics hold true with a small margin of error. Often times,
this is all we have to rely on when no other facts/data are
available.
Consortium Website
All data from crash testing and this presentation will be available at
http://tucrrc.utulsa.edu
Credentials
User: TUCRRCmember Password: TUCRRCpassword
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THANK YOU
Safe Travels.
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