collision avoidance at road intersections in the presence ... · collision avoidance at...
TRANSCRIPT
Collision Avoidance at Intersections in the Presence of Failures
Vladimir Savic, Elad M. Schiller and Marina Papatriantalou,
Computer Science and Engineering
Chalmers University of Technology
Motivation
• V2V enables better awareness of the surroundings,
• distant objects out of the sensing horizon
• V2V is prone to failures, delays and uncertainty of the participating nodes
• A fault-tolerant and affordable implementations are needed
The Intersection Crossing (IC) Problem
• Once a vehicle enters the capture area, there are no guarantees that it can avoid collision with another vehicle coming from a conflicting direction. Capture Area (CA)
Intersection
The Intersection Crossing (IC) Problem
• [safety] No two vehicles from conflicting directions are allowed to enter their the capture area
• [liveness] Eventually, all vehicles can cross the intersection
Capture Area (CA)
Intersection
Existing Solutions
Capture Area (CA)
Intersection
• Current proposals assume that the failure occurrences can be characterize, e.g., via a distribution• a bounded delay w.h.p.
• Such assumptions do not take into account abnormal behavior.• Once an unexpected failure
occurs, neither safety nor liveness is guaranteed
The Challenge
Capture Area (CA)
Intersection
• Communication fairness: a packet that is sent infernally often, is received infernally often
• No bound on the communication delay other than the assumption that it is an unknown finite number.
Our Contribution
• We propose a solution to the intersection crossing (IC) problem with V2V communication.
• We handle any finite number of packet failures.
• We provide:
• Numerical simulations
• An analysis based on a time diagram
• According to our results, based on a real data set, the crossing delay is only slightly increased even in the presence of highly correlated failures.
The System
• We consider two fully autonomous cars (C1, C2), equipped with V2V, GPS and IMU, aiming to cross a road intersection.
Capture Area (CA)
Intersection
The Protocol
We define the following V2V messages:
•MSGHB: periodic heart-beat (HB)
•MSGENTER: indication that car plans to enter the intersection
•MSGEXIT: indication that car plans to exit the intersection
Capture Area (CA)
Intersection
The Protocol
• Makes sure that both vehicles are aware of each other.
• Lets one of the vehicles cross the intersection after this decision was acknowledged by the other vehicle.
• Inform the other vehicle that the road is open after the first crossing.
Numerical simulations
• To analyze the delay caused by communication failures, we use the real measurements available in [1].
• Two scenarios:
• open-field (without any obstacles), and
• harsh (with many obstacles, such as tunnels and bridges)
[1] F. Bai, H. Krishnan, “Reliability analysis of DSRC wireless communication for vehicle safety applications,” in Proc. of IEEE Intelligent Transp. Systems Conf., Sept 2006.
Conclusions
• We proposed a technique for dealing with communication failures
• Using this technique, we device a fault-tolerant algorithm for intersection crossing
• We analyzed time diagrams and provided the numerical results in realistic situations that show that both safety and liveness are satisfied
Contact information
This presentation is based on a talked the Vladimir Savic gave in Intelligent Vehicles Symposium 2017: 1005-1012 with the title `Distributed algorithm for collision avoidance at road intersections in the presence of communication failures’
Contact person: Elad Michael Schiller
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