Anti-lock%20Brake%20System

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Anti-lock Brake System

• Group 2
• Presenters Christan Balnius,
• Zain Kazim, Mark Pulver
• Demo Given by Brian Lawnichak

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Unique Feature Distributed Control System (DCS)

• Enhances modularity of system
• Components of DCS
• Manager
• Wheel Monitors
• Wheel Cylinder Gnomes

http//members.tripod.com/waterdragon/boygnome.gi
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What DCS Supports

• Functionality of DCS
• Computes, recognizes, and responds to rapid
  deceleration
• Encapsulates per-wheel activity
• Sample scenario description
• Manager receives brake signal
• Manager signals Wheel Monitors
• Wheel Monitors compute deceleration
• Wheel Monitors signal Gnome

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Key Model State Diagram

• High-level state diagram showing concurrent
  processes
• It is key because
• Shows the major components of system
• Highlights concurrency
• We will decompose this further

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High-level State Diagram
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Key Model Revisited

• Now focusing on the Manager, which is the top
  level of the DCS
• Manager is key because
• Handles error testing
• Responds to signals from vehicle
• Sends signals to wheel monitors as appropriate
• State diagram highlights this behavior

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Manager State Diagram
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Critical Properties

• Safety properties
• If ABS fails, mechanical braking still works
• ABS activity never leads to spins
• Liveness properties
• If the car speed drops below 15 mph while
  braking, ABS becomes idle
• If a skid is detected above 15 mph, pressure is
  modulated on the wheel

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Promela and XSpin

• Verification Technique
• Modeled our state diagram in Promela
• Verified safety and liveness properties through
  use of LTL invariants
• Assertion and reachability tests were also
  performed

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Safety Property Verification

• If ABS fails, mechanical braking still works
• (Error -gt (Power Off Brake Not Pressed
  ltgt(Main Brake Valves Open, Relief Valves
  Closed)))
• XSpin verified that this property holds

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Liveness Property Verification

• If the car speed drops below 15 mph while
  braking, ABS becomes idle
• (Below Activation Speed -gt ltgt(Wheel Monitors
  Idle))
• XSpin verified that this property holds

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Demo of Prototype

• High-level features of User Interface
• Independent control of wheel speed and
  acceleration
• Changeable environmental factors
• Feedback on system-wide conditions with indicator
  lights
• Per-wheel information readout

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Scenario 1

• Single-wheel skid
• Press ignition button to start engine
• Increase system speed to 30 m/s
• Press brake button
• Decrease the speed on wheel 3 to 20 m/s

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Scenario 2

• Change-of-surface skid
• Press ignition button to start engine
• Increase system speed to 30 m/s
• Press brake button
• Initiate a panic brake by increasing system brake
  pressure to 200 kg
• Change road type from Pavement to Gravel