Simulating Vehicle Suspension with a Simplified Quarter-Car Model

​
car suspensionanimation
start / pause / reset
elapsed time in sec =
0
suspension parameters
damping coefficient: c
0.85
spring constant: k
0.165
mass: m
1
road condition
road bump height
0.1
bump frequency: fb
1
The simplified quarter-car suspension model is basically a mass-spring-damper system with the car serving as the mass, the suspension coil as the spring, and the shock absorber as the damper.
This Demonstration lets you explore the affect of different suspension parameters and road conditions on the vertical motion of the car.
The mathematics of the system are based on the differential equation of the spring-damper suspension:
ctx'-cty'+ktx-kty+mtx''0
, which, after a Laplace transform, results in the transfer function
G(s)=
cs+k
cs+k+m
2
s
.The Mathematica 8 functions TransferFunctionModel and OutputResponse were used to calculate the car movement with no need to solve the differential equation.

Details

Snapshot 1: very hard suspension with a light car gives excessive shaking
Snapshot 2: the damping ratio is 1 and gives optimal comfort
Snapshot 3: at resonant frequency, a maximum car movement is obtained

External Links

Critically Damped Simple Harmonic Motion (Wolfram MathWorld)
OutputResponse (Wolfram Documentation Center)
TransferFunctionModel (Wolfram Documentation Center)

Permanent Citation

Erik Mahieu
​
​"Simulating Vehicle Suspension with a Simplified Quarter-Car Model"​
​http://demonstrations.wolfram.com/SimulatingVehicleSuspensionWithASimplifiedQuarterCarModel/​
​Wolfram Demonstrations Project​
​Published: March 11, 2011