Automotive suspension performance simulation.ppt

Automotive suspension systems are a critical aspect of any vehicle's design, serving to optimize stability, handling, comfort, and safety. Whether it's cruising down the highway, navigating sharp turns on a mountain road, or tackling rugged terrain off-road, the suspension plays a pivotal role in ensuring a smooth and controlled ride. In this comprehensive exploration, we'll delve into the various types of automotive suspensions, their components, working principles, and the advancements shaping the future of suspension technology.

Evolution of Suspension Systems:
The development of automotive suspension systems dates back to the early days of automobile manufacturing. In the early 20th century, vehicles primarily featured rudimentary leaf spring setups, providing basic shock absorption and load-bearing capabilities. As automotive technology progressed, more sophisticated suspension designs emerged, including coil springs, torsion bars, and air suspensions.

Types of Suspension Systems:
Independent Suspension:

Independent suspension systems allow each wheel to move independently, minimizing the transfer of motion between wheels. This setup enhances traction, stability, and overall ride quality.
Common types of independent suspensions include double wishbone, MacPherson strut, and multi-link setups.
Dependent Suspension:

Dependent suspensions connect the wheels on each axle, causing them to move in tandem. While simpler and more cost-effective, dependent suspensions typically offer inferior handling and ride comfort compared to independent setups.
Examples of dependent suspensions include solid axle and torsion beam configurations.
Air Suspension:

Air suspension systems utilize air-filled rubber bags or bellows in place of traditional coil or leaf springs. These systems offer adjustable ride height and stiffness, allowing drivers to tailor their vehicle's handling characteristics to suit different driving conditions.
Air suspension is commonly found in luxury vehicles and heavy-duty trucks, where comfort and load-carrying capacity are paramount.
Active Suspension:

Active suspension systems employ advanced electronic controls to continuously adjust damping forces, ride height, and other parameters in real-time. By actively responding to changing road conditions and driver inputs, active suspensions can enhance both performance and comfort.
While initially limited to high-end luxury and performance vehicles, active suspension technology is becoming increasingly accessible across a wider range of vehicle segments.
Components of Suspension Systems:
Springs:

Springs are the primary load-bearing components of a suspension system, supporting the vehicle's weight and absorbing road irregularities. Common spring types include coil springs, leaf springs, and air springs.
Dampers (Shock Absorbers):

Dampers control the oscillations of the springs, damping out excessive motion and preventing the vehicle from bouncing uncontrollably. Shock absorbers diss

1. Suspension Design
Part 1
Rob Shanahan 11-15-05

2. 2
Introduction
What is an Automotive Suspension?
An Automotive Suspension is the system of parts that give
a vehicle the ability to maneuver.
It is a 3 Dimensional Four Bar Linkage
What does a suspension do?
“The job of a car suspension is to maximize the friction
between the tires and the road surface, to provide steering
stability with good handling” HowStuffWorks.com

3. 3
Basic Suspension Terminology
Ride Height
Bump / Droop
Camber
Caster
Toe In / Out

4. 4
Ride Height, Bump & Droop
Ride Height
The neutral / middle
position of the
Suspension
Bump
When the wheel
moves upwards
Droop
When the wheel
moves downwards

5. 5
Camber
Tires generate more
cornering force with
a small amount of
negative camber
Camber changes as
suspension moves
up (bump) and
down (droop)

6. 6
Caster
Shopping cart action
Causes self-
centering action in
the steering
More caster results
in more camber as
front wheels are
turned

7. 7
Toe-in or Toe-out
Toe-in results is
inherently stable
Toe-out is inherently
unstable
Race cars often use
front toe-out, & rear
toe-in

8. 8
Common Suspension Designs
Beam Axle
Swing Axle
De Dion
Double Wishbone /
Unequal Length A-arm

9. 9
Beam Axle
Around since horse
and chariot days
Always keeps wheels
parallel
Often used in rear
Rarely used in front
OK on smooth tracks

10. 10
Swing Axle
Often used on VW
based off road cars
Simple and rugged
Camber curve too
steep
Only adjustment you
can make is ride
height

11. 11
De Dion
Essentially a beam
axle with the diff
now sprung weight
Keeps wheels
parallel
Relatively light
weight
Better on smooth
tracks

12. 12
Double Wishbone
Lightest weight
Lowest unsprung
mass
Greatest
adjustability

13. 13
Basic Vehicle Dynamics
Part 2
What is Vehicle Dynamics?
The understanding and study of how a
vehicle and its components move and react

14. 14
Yaw, Pitch, and Roll
Same terminology
as aircraft
X is the longitudinal
axis
Yawing refers to
normal change of
direction
Pitching is dive or
squat

15. 15
Understeer
Front end of the car
“washes out” or doesn’t
“turn in”
NASCAR boys call it
“push” or “tight”
Safe, because lifting off
throttle reduces it
Most road cars have a
ton of it

16. 16
Oversteer
Rear end of car slides out
NASCAR boys call it “loose”
Excessive application of
power can cause oversteer
Throttle induced oversteer
is never the fast way
around a corner

17. 17
Weight Transfer
Occurs anything the vehicle
accelerates or decelerates
Cornering force Fc will
cause weight to transfer
from the inside to outside
tires
Braking and accelerating
forces cause a similar front
and rear weight transfer

18. 18
Roll Center
A geometric construct
Represents the instantaneous
point about which the sprung
mass will rotate due to cornering
forces
Roll center moves as suspension
travels
Goal of any suspension designer
is to minimize Roll Center
Migration

19. 19
Roll Couple
Distance from roll center
to CG is key
Low roll center results in
more roll for a given
lateral acceleration
Most designs use a low
roll center to reduce
jacking forces

20. 20
Anti-dive
Purely geometric method
to reduce pitch movement
Reduces suspension
compliance over bumps
No longer in favor with
formula car and sports
racers
Might work well for Baja

21. 21
Bump Steer
Caused when toe
changes as suspension
moves up and down
Causes car to react
unexpectedly over
bumps and in roll
Sometimes used
intentionally, but be
careful

22. 22
Tire Slip Angle
Angle between the
centerline of the
wheel and the actual
path
Tires generate
highest cornering
forces at a certain
slip angle

23. 23
Slip Angle vs. Grip
Grip is highest a set angle,
then falls off as the slip
angle increases
Sharper peak will give a less
predictable breakaway
Radial tires typically have a
steeper slope than bias ply

24. 24
Friction Circle
Plots the theoretical
limits of adhesion in
2 axes
Great tool for
analyzing driver to
driver variation
G-analyst is a cheap
tool for this

25. 25
Friction Circle, cont.
Illustrates the trade off
between cornering and
braking/accelerating
The driver that follows the
path closest to the outside
of the circle wins

26. 26
Car Balance
A well balanced car will exhibit
both understeer and oversteer at
different points on the course and
at corner entry and exit
A good driver can change his
technique to change the basic
oversteer/understeer balance