Steering%20Behaviors%20for%20Autonomous%20Vehicles%20in%20Virtual%20Evironments

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Steering Behaviors for Autonomous Vehicles in
Virtual Evironments

• Hongling Wang
• Joseph K. Kearney
• James Cremer
• Department Of Computer Science
• University of Iowa
• Peter Willemsen
• School of Computing
• University of Utah

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Focus

• Control of Autonomous Vehicles in VE
• Ambient traffic
• Principal roles in scenarios
• Importance of Road Representation
• Frame of reference
• Natural coordinate system
• Intersection and Lane Changing Behaviors
• Complex interactions among vehicles
• Limits of independent control

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Motivation

• VE as Laboratories for Studying Human Behavior
• Developmental differences in road crossing
• The influence of disease, drugs, and disabilities
• Design of in-vehicle technology
• Cell phones, navigation aids, collision warning

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Bicycle Simulator Video
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Gap Acceptance in the Hank Bicycle Simulator
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Related Work

• Flocking
• Complex group behavior from simple rule-based
  behaviors (Reynolds)
• Hierarchical Distributed Contol
• Independent, goal-oriented sub-behaviors
  (Badler et al. Blumberg and Galyean Cremer,
  Kearney, and Papelis)
• Driving
• Simulation (Donikian Lemessi)
• ALV (Coulter, Sukthankar Wit, Crane, and
  Armstrong)
• Human Driving Behavior (Ahmed Boer, Kuge, and
  Yamamura Fang, Pham, and Kobayashi Salvucci and
  Liu)

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Roadway Modeling

• Roads as Ribbons
• Oriented Surface
• Smooth Strips
• Twist and turn in space
• Central Axis
• Arc-length parameterized curve
• Twist Angle
• Linked through Intersections

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Ribbon

• Ribbon coordinate system
• Distance, Offset, and loft (D,O,L)
• Egocentric frame of reference
• Efficient Mapping (D,O,L) (X,Y,Z)

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IntersectionsWhere Roads Join

• Shared regions
• Non-oriented
• Corridors connect incoming and outgoing lanes
• Single lane ribbons
• Annotated with right-of-way rules

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Ribbon to Ribbon Transitions

• Problem Tangle of Ribbons
• Bookkeeping Tedious and Error Prone
• Possible switch in orientation
• Possible shift in alignment
• Solution Paths
• Composite ribbons

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Path

• One-lane Overlay
• Removes transitions between ribbons
• Immediate Plan of Action
• Highly dynamic
• Natural frame of reference

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Distributed Control

• Multiple, Independent Controllers
• Each responsible for some aspect of behavior
• e.g. Cruising, Following
• Compete for control
• Control Parameters
• Acceleration
• Steering Angle

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Road Tracking

• Non-holonomic constraint
• Rolling wheels
• Move on a circle
• Pursuit point control
• Steer to a point on the path
• Look-ahead distance

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Controlling Speed

• Cruising Proportion Control
• Following Proportional Derivative Controller

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Intersection Behavior

• Gates access to shared regions
• Decision
• Go / No Go
• Action
• stop at stopline

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Gap Acceptance

• Based on Interval Analysis
• Right-of-way rules encoded in DB
• Corridors as resources
• Compare crossing intervals

c0
c2
c1
time
tenter
texit
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Intersection Exceptions

• Problem deadlock
• Double blocked threats
• Solution
• Recognition and response
• Problem starvation
• Unending stream of opposition
• Solution
• Guaranteed progress

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Whats missing?

• Where do paths come from?
• Vehicles meander
• Pick corridors
• Add outgoing road
• No goal seeking behavior
• Need directions
• Turn right at the first intersection,
• drive through two intersections,
• and then turn left.

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Route

• A succession of roads and intersections
• Like MapQuest Directions
• A global, strategic goal
• The path must conform to the route
• May require lane changes

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Stages of Lane Changing

• Motivation
• Why change lanes?
• Decision
• Choosing a target lane
• Deciding when to go
• Action
• How to change lanes?

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• Motivation to Change Lanes
• Discretionary Lane Change (DLC)
• to improve driving conditions (e.g. speed,
  density)
• Mandatory Lane Change (MLC)
• to meet destination requirements (e.g. lane
  termination)
• Decision to Initiate a Lane Change
• Best conditions (e.g. flow)
• Gap Acceptance
• Lead gap
• Lag gap

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Lane Changing Action

• Shift Pursuit Point
• Proportional Derivative Controller
• Speed Coupling

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Behavior Combination

• Combine accelerations from
• Cruising behavior
• Following behavior
• Intersection behavior
• Combine steering angle from
• Tracking behavior
• Lane changing behavior

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Interactions Between Controllers

• Problem impeded progress
• Following prevents overtaking
• Solution
• Reduce following distance
• Stiffen controller
• Problem unveiled threat
• Appearance of leader in new lane
• Solution
• Split attention follow 2 leaders

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Summary

• An accurate, efficient, robust roadway model
• Ribbon network
• Arc length parameterization
• Efficient mapping between ribbon and Cartesian
  coordinates
• A framework for modeling behaviors
• Ribbon based tracking
• Path based behaviors
• Route as a strategic goal

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Future Work

• Pedestrians
• Modeling non-oriented navigable surfaces
• (e.g. intersections)
• Pursuit Point Control
• Behavioral Diversity

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Acknowledgments

• NSF Support INT-9724746, EIA-0130864, and
  IIS-0002535
• Contributing students, staff, faculty
• Jodie Plumert Geb Thomas
• David Schwebel Pete Willemsen
• Penney Nichols-Whitehead HongLing Wang
• Jennifer Lee Steffan Munteanu
• Sarah Rains Joan Severson
• Sara Koschmeder Tom Drewes
• Ben Fraga Forrest Meggers
• Kim Schroeder Paul Debbins
• Stephanie Dawes Bohong Zhang
• Lloyd Frei Zhi-hong Wang
• Keith Miller
  Xiao-Qian Jiang