CAMP-G SIMULATION OF CAR SUSPENSION SYSTEM

ME -270 ADVANCE COMPUTER AIDED DESIGN OF DYNAMIC SYSTEM

PROF. J. GRANDA

FALL 2007FINAL PROJECT

DATE : 21 DECEMBER 2007

CREATED BY PRAMOD KRISHNANI

PAWAN SAGAR

Sketch Model

Bond Graph

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

CASE 1 :: Change velocity of Car

Velocity changed to10 mph 20 mph40 mph60 mph 100 mph

Graph of Displacement of Rear and Front suspension

Velocity of a car = 10 mph

0 5 10 15 20 25 30 35 40-5

0

5

10

15 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

5

10

15 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Velocity of a car = 20 mph

0 5 10 15 20 25 30 35 40-5

0

5

10

15 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

5

10

15 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Velocity of a car = 40 mph

0 5 10 15 20 25 30 35 40-5

0

5

10

15 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

5

10

15 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Velocity of a car = 60 mph

0 5 10 15 20 25 30 35 40-10

0

10

20 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

5

10

15 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Velocity of a car = 100 mph

0 5 10 15 20 25 30 35 40-10

0

10

20 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

5

10

15 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

CASE 2 :: Design of Spring and Damping properties

ObservationNo

Velocity (mph)

Kf (N/m) Rf (N-s/m)

Kr (N/m) Rr (N-s/m)

1 100 100 50 100 50

2 100 500 250 500 250

3 100 1000 50 1000 50

4 100 2000 10 2000 100

5 100 2000 1800 2000 1800

Observation Number 1

0 5 10 15 20 25 30 35 40-10

0

10

20 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

5

10

15 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 2

0 5 10 15 20 25 30 35 40-4

-2

0

2

4 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

1

2

3 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 3

0 5 10 15 20 25 30 35 40-5

0

5 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 40-2

0

2

4

6 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 4

0 5 10 15 20 25 30 35 40-4

-2

0

2

4 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 40-1

0

1

2

3 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 5

0 5 10 15 20 25 30 35 40-0.5

0

0.5 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15

0.3

0.4

0.5

Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

CASE 3 :: Changes made in position of Center of Gravity

Observation

Velocity

(mph)

Scenario a (meter

s)

b (meter

s)

Kf (N/m)

Rf (N-

s/m)

Kr (N/m

)

Rr (N-

s/m)

1 100 Moving C.G.

closer to Front Axle

0.3 0.7 1000 300 1000 300

2 100 0.2 0.8 1000 300 1000 300

3 100 Moving C.G.

closer to Rear Axle

0.7 0.3 1000 300 1000 300

4 100 0.8 0.2 1000 300 1000 300

Moving C.G. closer to Front Axle

Observation Number 1

0 5 10 15 20 25 30 35 40-2

-1

0

1

2 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

1

2

3 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 2

0 5 10 15 20 25 30 35 40-1

0

1

2

3 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

1

2

3 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Moving C.G. closer to Rear Axle

Observation Number 3

0 5 10 15 20 25 30 35 40-3

-2

-1

0

1 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

1

2

3 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 4

0 5 10 15 20 25 30 35 40-3

-2

-1

0

1 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

1

2

3 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

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 (N-s/m)

1 100 Lower Bump

-12 0 1000 300 1000 300

2 100 0 -12 1000 300 1000 300

3 100 -12 -12 1000 300 1000 300

4 100 Upper Bump

12 0 1000 300 1000 300

5 100 0 12 1000 300 1000 300

6 100 12 12 1000 300 1000 300

Lower Bump

Observation Number 1

0 5 10 15 20 25 30 35 40-1

0

1

2 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

1

2

3 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 2

0 5 10 15 20 25 30 35 40-2

-1

0

1

2 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

1

2

3

4 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 3

0 5 10 15 20 25 30 35 40-1

0

1

2 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

2

4

6 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Upper Bump

Observation Number 4

0 5 10 15 20 25 30 35 40-4

-2

0

2 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

0.5

1

1.5

2 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 5

0 5 10 15 20 25 30 35 40-4

-2

0

2 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 400

0.5

1

1.5 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Observation Number 6

0 5 10 15 20 25 30 35 40-4

-2

0

2 Displacement of the front axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

0 5 10 15 20 25 30 35 40-0.5

0

0.5

1

1.5 Displacement of the rear axle

Dis

pla

cem

ent

(mete

rs)

Time (seconds)

Case 5 :: Car with consideration of the Passenger

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 = 0.000001 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

Results of case 5

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

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.