1. Camp-g simulation of car suspension system ME -270 Advance Computer aided design of dynamic system Prof. j. granda FALL 2007 final project date : 21 december Created By Pramod Krishnani Pawan Sagar

2. Sketch Model

3. Bond Graph

4. Initial Parameters Moment of Inertia of Car = J = 20 K-m2
Mass of Car = 200 Kg
Distance of front axle from the center of gravity = a = 0.5 meter
Distance of Rear Axle from the center of gravity = b = 0.5 meter
Spring factor at rear wheel suspension = Kr = 1000 N/m
Damping factor at rear wheel suspension = Rr = 300 N-s/m
Spring factor at front wheel suspension = Kf = 1000 N/m
Damping factor at front wheel suspension = Rf = 300 N-s/m
Velocity input at the rear wheel due to bump = Vr_in = 0 m/s
Velocity input at the front wheel due to bump = Vf_in = 0 m/s

5. CASE 1 :: Change velocity of Car
Velocity changed to
10 mph
20 mph
40 mph
60 mph
100 mph

6. Graph of Displacement of Rear and Front suspension
Velocity of a car = 10 mph

7. Velocity of a car = 20 mph

8. Velocity of a car = 40 mph

9. Velocity of a car = 60 mph

10. Velocity of a car = 100 mph

11. CASE 2 :: Design of Spring and Damping properties
Observation No
Velocity (mph)
Kf (N/m)
Rf (N-s/m)
Kr (N/m)
Rr (N-s/m) 1
100 50 2
500
250 3
1000 4
2000 10 5
1800

12. Observation Number 1

13. Observation Number 2

14. Observation Number 3

15. Observation Number 4

16. Observation Number 5

17. CASE 3 :: Changes made in position of Center of Gravity
Observation
Velocity (mph)
Scenario
a (meters)
b (meters)
Kf (N/m) Rf
(N-s/m)
Kr (N/m) Rr 1
100
Moving C.G. closer to Front Axle
0.3
0.7
1000
300 2
0.2
0.8 3
Moving C.G. closer to Rear Axle 4

18. Moving C.G. closer to Front Axle

19. Observation Number 1

20. Observation Number 2

21. Moving C.G. closer to Rear Axle

22. Observation Number 3

23. Observation Number 4

24. Case 4 :: Giving a Bump to the Vehicle
Observation
Velocity (mph)
Scenario
Vf (m/s)
Vr (m/s)
Kf (N/m) Rf
(N-s/m)
Kr (N/m) Rr 1
100
Lower Bump
-12
1000
300 2 3 4
Upper Bump 12 5 6

25. Lower Bump

26. Observation Number 1

27. Observation Number 2

28. Observation Number 3

29. Upper Bump

30. Observation Number 4

31. Observation Number 5

32. Observation Number 6

33. Case 5 :: Car with consideration of the Passenger

34. Initial Parameters Moment of Inertia of Car = J = 20 K-m2
Mass of Car = 200 Kg
Mass of Man = 20 Kg
Distance of front axle from the center of gravity = a = 0.5 meter
Distance of Rear Axle from the center of gravity = b = 0.5 meter
Distance of man from the center of gravity = c = 0.3 meter
Spring factor below the seat of the man = Ks = N/m
Spring factor at rear wheel suspension = Kr = 1000 N/m
Damping factor at rear wheel suspension = Rr = 300 N-s/m
Spring factor at front wheel suspension = Kf = 1000 N/m
Damping factor at front wheel suspension = Rf = 300 N-s/m
Velocity input at the rear wheel due to bump = Vr_in = 0 m/s
Velocity input at the front wheel due to bump = Vf_in = 0 m/s

35. Results of case 5

36. Conclusion
From Case 1, we can say that as we increase the velocity from 10 to 100 mph the displacement of the front axle suspension and the rear axle suspension increases. But comparing the rear axle suspension with the front axle suspension, we can say that the rear axle is always having more displacement than the front axle suspension displacement.
From Case 2, we have designed the best Damper and spring properties for the case of a car having a weight of 200 Kg of weight. The Kf =Kr=2000 N/m,Rf=Rr =1800 N-s/m

37. Conclusion
From Case 3, we changed the center of gravity of the car towards the forwards position and we could see that the suspension at the rear portion was less loaded and thus gave less oscillations than the front one. The opposite happened for the case when we shifted the center of gravity towards the rear axle.
From Case 4, we gave a lower bump and we could see that there was a sudden oscillation increase at the starting time and it kept constant for some time. The same results happened for the upper bump but the graph was having oscillation in the positive direction.
From Case 5, we studied the oscillation of the seat of the passenger and we could conclude that with the initial parameters the oscillation in the seat will nullify after 12 to 13 seconds.