Transcript Mechantronic Simulation of Simple Brake System

E 579
Bond Graph Simulation of Simple
Brake System
Instructor
Dr Shuvra Das
By
Harish Nair
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Bond graph model of simple brake
system
Contents
• Introduction to brake systems
• Bond graph models
• Results
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Introduction to brake systems
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Purpose of Brake System
The basic functions of a brake system are
to slow a vehicle’s speed, to maintain it’s
speed during downhill operation, and to
hold a vehicle stationary after it has come
to a complete stop
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Brake System Components
•
•
•
•
All brake systems can be divided into four
basic subsystems.
Energy source
Apply system
Energy transmission system
Wheel or foundation brakes
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system
Types of energy source
•
•
•
•
•
•
Muscular driver pedal effort
Brake boost assist systems
Power brake systems
Surge brakes
Electric brakes
Spring brakes
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system
Energy Transmission Medium
•
•
•
•
•
Mechanical brakes
Hydraulic brakes
Air brakes
Electric brakes
Mixed brakes
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Type of Dual Split System
• Single-circuit systems
Uses only one circuit to transmit
braking energy to the wheel brakes.
• Dual Circuit systems
Uses two or more circuits to transmit
braking energy to the wheel brakes.
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Typical Brake System components
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Components of the brake system
•
•
•
•
•
•
Brake pedal
Vacuum booster
Master cylinder
Hoses
Brakes
Rotors
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Type of Friction Brakes
•
•
Automotive friction brakes are grouped
according to their basic design into two
classes.
Drum brakes
Use brake shoes that are pushed out in a
radial direction against a brake drum.
Disc brakes
Use pads that are pressed axially against a
rotor or disc.
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Disc Brakes
The rotor or disc rotates inside the caliper.
The wheel cylinder pistons force the pads
against the rotor and produce brake
torque.
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Bond graph model of simple brake
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Working of a Disc Brake System
When the brake is applied, the force is
magnified by both mechanical leverage
and also by hydraulic magnification. Brake
fluid under pressure enters the caliper and
causes the braking action.
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Bond Graph Model
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Bond Graph Model
What was used?
• Transformers
• Transformers
• And more transformers!!!
All values used are from standard
calculation values for a SUV. The caliper
used is a twin piston one.
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Bond Graph
R
Brake_coeff
R
I
Road_friction_coeff
Se
Se1
TF
Leverage
TF
Booster
TF
1
Hydraulic_Multiplier
OneJunction3
TF
Drag_force
TF
braking_torque
Wheel_mass
1
MSe
OneJunction1
MSe1
TF
C
TF6
C1
SignalGenerator1
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Force amplification system
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Se
238.51 N
Leverage
3.7
Booster
7.365
Hydraulic
Multiplier
14.35
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system
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Brake_coeff
1.5
C1
Very low up to
1mm
Very high after
that
Bond graph model of simple brake
system
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Drag_force (Fd)
2*brake coeff
Braking_torque
Fd * Effective
radius(350mm)
Bond graph model of simple brake
system
Wheel Subsystem
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New Bond graph
R
Road_friction_coeff
MSe
MSe2
TF
Leverage
TF
Booster
TF
0
Hydraulic_MultiplierZeroJunction1
MR
MR1
1
OneJunction2
TF
Drag_force
TF
braking_torque
1
MSe
OneJunction1
MSe1
TF
TF6
I
Wheel_mass
SignalGenerator2
Modulated Resistance
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SignalGenerator1
Results
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Angular Displacement of wheel Vs Time
p.f
p.e
300
200
100
0
-100
0
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5
10
15
20
time {s}
25
Bond graph model of simple brake
system
30
35
40
Zoomed View
Angular Displacement of wheel Vs Time
p.f
p.e
4
2
0
-2
-4
-6
-8
24.9
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24.95
25
time {s}
25.05
Bond graph model of simple brake
system
25.1
25.15
Discussion
• The model works fine in that the wheel
stops eventually.
• However the system response was
dominated by transients.
• The discontinuous spring element is the
main reason for the transient
phenomenon.
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Bond Graph 2 result
Wheel Displacement Vs Time
p.f
10
5
0
-5
0
0.1
0.2
0.3
time {s}
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0.4
0.5
Discussion
• The wheel stops in around 0.5 sec which
is a more realistic scenario.
• This is probably a better way to do the
simulation.
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Bond graph model of simple brake
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Conclusion
To get a better result, we need to model
the system in such a form that we get a
constant brake torque at the pads instead
of an on and off application of the pads to
the rotor.
Bond Graph 2 seems to have solved the
problem. But the model is still unclear to
me.
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References
• Continental Teves
• “Brake design and safety” by Rudolf
Limpert
• Howstuffworks.com for figures
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Bond graph model of simple brake
system