steering behaviors for autonomous vehicles in virtual evironments hongling wang joseph k. kearney...
TRANSCRIPT
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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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Intersections—Where 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
)()( vKsKfa f
vfp
)( vvKca d
cp
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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
time
c0
tenter texit
c2c1
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Intersection Exceptions Problem: deadlock
Double blocked threats• Solution:
Recognition and response
Problem: starvationUnending stream of opposition
• Solution: Guaranteed progress
)2/(2 sva
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What’s 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
)()( oKotoKo LC
vLCp
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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 progressFollowing prevents overtaking
• Solution: Reduce following distance
Stiffen controller
Problem: unveiled threatAppearance 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 WillemsenPenney Nichols-Whitehead HongLing WangJennifer Lee Steffan MunteanuSarah Rains Joan Severson Sara Koschmeder Tom DrewesBen Fraga Forrest MeggersKim Schroeder Paul DebbinsStephanie Dawes Bohong ZhangLloyd Frei Zhi-hong WangKeith Miller Xiao-Qian Jiang