[자율주행 스터디] Introduction to Self-Driving cars - Week 2-2

Week 2 - Self-Driving Hardware and Software Architectures

Course info.

• https://www.coursera.org/learn/intro-self-driving-cars?
  • UNIVERSITY OF TORONTO

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Lesson 2 : Hardware Configuration Design

Contents

• Sensor coverage requirements for differenct scenarios
  • Highway driving
  • Urban driving
• Overall coverage, blind spots

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Sensors

• Camera for appearance input
  • Stereo camera for depth information
• Lidar for all whether 3D input
• Radar for object detection
• Ultrasonic for short-range 3D input
• GNSS/IMU, Wheel odometry for ego state estimation

Assumptions

• Aggressive deceleration = $5m/s^2$
• Comfortable deceleration = $2m/s^2$
  • This is the norm, unless otherwise stated
• Stopping distance = $d = v^2/2a$

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Where to place sensors?

• Need sensors to support maneuvers within our ODD
• Broadly, we have two driving environments

-	Highway	Urban/Residential
Traffic Speed	High	Low-Medium
Traffic volume	High	Medium-High
# of lanes	More	2-4 typically
Other Features	Fewer, gradual, curves; merges	Many turns and intersections

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Highway Analysis

• Broadly, 3 kinds of maneuvers

  • Emergency stop
  • Maintain speed
  • Lane change

• Emergency stop

  • If there is a blockage ahead, we want to stop in time.
  • To avoid collision, either we stop or change lanes
    • Longitudinal coverage
      • Assume we are speeding at 120km/h
        • -> Stopping distance could be 110m (aggressive deceleration)
    • Lateral coverage
      • At least adjacent lanes, since we may change lanes to avoid a hard stop
        • 3.7m wide in North America

• Maintain speed (during vehicle following)

  • Need to sense the vehicle in our own lane
    • Both their relative position and the speed are importatnt to maintatin a safe following distance
  • Relative speed are typically less than 30km/h
    • Longitudinal coverage
      • 2 seconds in nominal conditions
        • Usually defined in units of time for human drivers
      • At least 100m in front in aggressive deceleration of the lead vehicle
      • Both vehicles are moving, so don't need to look as far as emergency stop case

• Maintatin speed (with Merge)

  • Lateral coverage
    • Adjacent lanes would be preferred for merging vehicle detection
      • To track vehicles in adjacent lanes
        • A wide 160 to 180 degree field of view is required
        • A range of 40 to 60 meters is needed to find space between vehicles

• Lane change

  • Consider this possible lane change scenario
    • Longitudinal coverage
      • Need to look forward to maintain a safe distance
      • Need to look behind to see what rear vehicles are doing
    • Lateral coverage
      • Laterally, we need to look not just in the adjacent lanes, but probably further
      • Need wider sensing

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Urban Analysis

• Broadly, 6 kinds of maneuvers

  • Similar to highway analysis
    • Emergency stop
    • Maintain speed
    • Lane change
  • Additional consideration in Urban Analysis
    • Overtaking
    • Turning, crossing at intersections
    • Passing round abouts

• Overtaking (a parked car)

  • Longitudinal coverage
    • if overtaking a parked or moving vehicle, need to detect on coming traffic beyond point of return to own lane
      • Wide short-range sensors to detect the parked car
      • Narrow long-ragne sensors to identify if oncoming traffic is approaching
  • Lateral coverage
    • Always need to observe adjacent lanes
    • Need to observe additional lanes if other vehicles can move into adjacent lanes

• Intersections

  • Observe beyond intersection for approaching vehicles, pedestrian crossings, clear exit lanes
  • Requires near omni-directional sensing for arbitrary intersection angles

• Roundabouts

  • Longitudinal coverage
    • Due to the shape of the roundabout, need wider field of view
  • Lateral coverage
    • Vehicles are slower than usual, limited range requirement