Vehicle Crash Test

Dong-Un Sul

Dr. Granda

ME 270

Design Requirements

• Design appropriate seat belts.• Head of Dummy does not travel more than

1 meter in the vehicle.• Driver should be safe when vehicle crash

test performed.• Build Bond graph for the model assigned.• Compare outputs from m.files with the

results come out from using simulink in matlab.

Step 1Building bond graph

Step 2

• Obtain the differential equation by hand of the system in the Cauchy form

• By using campgsym.m, verify the hand derivation

• Following scanned notes show the differential equations that I derived from the bond graph drawn above.

State Space form

• From the differential equations verified by matlab, now state-space matrix can be created by hand.

• State-Space form driven from matlab (campgsym.m) is matched with that which is the next coming slide.

Critical Max. Velocity

• When the vehicle travels more than 30mph, dummy can be injured by the force generation.

• Therefore, parameters of seat belts and bumper must be adjusted in order to avoid driver’s injury when the vehicle travels over 30 mph.

No seat belts

• Without a seat belt, it takes less than a second for dummy to hit the windshield of the vehicle.

• Following graph shown below indicates how fast dummy gets out of the vehicle when crashed.

25 mph 40 mph 55 mph

0.105 s 0.072 s 0.057 s

Graphs

Simulink Scope

Best Design• For the best design of seat belts, spring

constant of bumper should be decreased, and damper R value also should be smaller.

• If C value of seat belts is the same, R value should go up to 2000.

• C3 = 1/50000 ; R4 =9000 ; • I6 = 1500 ; C9 = (1/10000) ; • R10 = 2000 ; I11 = 100 ;

Conclusion

• Bond graph helps engineers save their efforts without setting complicated mathematical equations about actual problems.

• Matlab can provide a good means to measure different parameters (i.e. velocity, force, so on).

• Matlab will provide very accurate data that I have expected if I know well how to program in it.

• However, unlike other software, Matlab sometimes generates some unfixable errors.