E 579 Bond Graph Simulation of Simple Brake System

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E 579Bond Graph Simulation of Simple Brake
System

• Instructor
• Dr Shuvra Das
• By
• Harish Nair

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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 vehicles speed, to maintain its 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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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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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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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
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Force amplification system
Se 238.51 N
Leverage 3.7
Booster 7.365
Hydraulic Multiplier 14.35
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Brake_coeff 1.5
C1 Very low up to 1mm Very high after that
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Drag_force (Fd) 2brake coeff
Braking_torque Fd Effective radius(350mm)
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Wheel Subsystem
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New Bond graph
Modulated Resistance
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Results
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Zoomed View
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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
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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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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