october 21 – bnaic 2004 jonne zutt and cees witteveen multi-agent transport planning delft...
TRANSCRIPT
October 21 – BNAIC 2004
Jonne Zutt and Cees Witteveen
Multi-Agent Transport Planning
Delft University of Technology
October 21 – BNAIC 2004
Contents
• Transportation planning
• Model
• Problem description
• Methods
• Results
• Future work
October 21 – BNAIC 2004
Transportation planning
• Guide-path design• Estimating optimal
number of vehicles• Vehicle maintenance• Order allocation• Idle-vehicle positioning• Vehicle routing• Conflict-resolution
October 21 – BNAIC 2004
Transportation planning
• Guide-path design• Estimating optimal
number of vehicles• Vehicle maintenance• Order allocation• Idle-vehicle positioning• Vehicle routing• Conflict-resolution
Strategic
Tactic
Operationalminutes
hours
months
October 21 – BNAIC 2004
Model
Auctioneeragent
Transportagent
Transportagent
Transportagent
Customeragent
Transportresource
Transportresource
Transportresource
speedcapacity
max. speedcapacitydistance
cooperativecompetitive
October 21 – BNAIC 2004
Model: incidents
• Events that disrupt regular plan execution and generally require re-planning
• Examples: customers that change or retract transportation orders, unpredictable congestion, vehicle break-down, communication failure
• Incidents are generated proportional to the resources. Pfail = 0.x means each resources is expected to fail x·10% of the time.
October 21 – BNAIC 2004
Problem description
• Find conflict-free routes for the operational agents such as to execute all orders, to maximize rewards and to minimize costs
• Maintain feasible plans even when incidents occur
October 21 – BNAIC 2004
Conflicts
1. Resources have limited capacity
A B C
2. Instantaneous exchange
ABD
Time
A B C
AB
Time
D
October 21 – BNAIC 2004
Method
• Do (partial) order assignment
• While agents are not ready– Compute traffic-aware shortest path– Agent compete who schedules first (P1)– Winner schedules n resources (P2)
• If current order rewards are below threshold, agent tries to reroute (P3)
October 21 – BNAIC 2004
Method: traffic-aware shortest path
• Agents know which time-windows are in use by other agents per resource
• Run an A* algorithm: store routes on open list, check for conflict when appending to candidate route
• Process is guaranteed to terminate and find the traffic-aware shortest path
October 21 – BNAIC 2004
Method: agent selection functions (P1)
• RandomProvides a baseline for the others
• DelaysAgent with maximum wait time first
• DeadlinesAgent with most strict deadlines first
• PenaltiesAgent with lowest planned reward first
October 21 – BNAIC 2004
Method: resource block-size (P2)
• How many resources (fraction of route) are scheduled after the agent is selected by the agent selection function?
• Hypothesis: a small block-size slightly increases performance but also increases computation time
October 21 – BNAIC 2004
Experiments
• 10 transport networks with 25 resources
• 10 sets of transportation orders with 75 random orders each
• 2 different sets of agents with 30 randomly located agents each
• Incidents with failure probability 0, 0.1 and 0.2.
October 21 – BNAIC 2004
Agent selectionA
vera
ge s
um
of
del
iver
y p
enal
ties
No incidents Pfail = 0.1 Pfail = 0.2
0 reroutes 1 reroute 0 reroutes 1 reroute 0 reroutes 1 reroute
1. Random2. Delays3. Deadlines4. Penalties
0
500
1
000
150
0 2
000
250
0 3
000
350
0
October 21 – BNAIC 2004
Block size
No incidents Pfail = 0.1 Pfail = 0.2
0 1 1 1 1 1 10 0 0 0 01 1 1 1 1 1
Ave
rage
su
m o
f d
eliv
ery
pen
alti
es
2 2 4 6 ∞ 2 4∞ 2 ∞ 2 ∞6 ∞ 2 4 6 ∞
1. max. number of reroutes2. block size
0
100
0
2
000
300
0
October 21 – BNAIC 2004
Time for different block sizes
No incidents Pfail = 0.1 Pfail = 0.2
2 2 4 6 ∞ 2 4∞ 2 ∞ 2 ∞6 ∞ 2 4 6 ∞0 1 1 1 1 1 10 0 0 0 01 1 1 1 1 1
Ave
rage
cp
u t
ime
0
1
2
3
4
5
6
71. max. number of reroutes2. block size
October 21 – BNAIC 2004
Conclusions
• Rerouting instead of static routing improves performance
• Prioritizing agents according to the order’s deadlines seems to work well (on random network topologies)
• Smaller block size is better, at the cost of some extra computation time
October 21 – BNAIC 2004
Future work
• Experiments for different network topologies
• (Market-based) distributed version
• Effect of coordination strategies
October 21 – BNAIC 2004
Questions
• CABS project:http://cabs.ewi.tudelft.nl
• My homepage: http://dutiih.twi.tudelft.nl/~jonne
• My email: [email protected]