Transcript MINEFIELD MODELING ISSUES

MINEFIELD MODELING ISSUES
MINWARA 6
9-13 May 2004
Alan Washburn
Naval Postgraduate School
Operations Research Department
(831) 656-3127
[email protected]
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MY CONTENTION…
• Clearing a minefield is a complicated process that
should be aided by computers.
• The design of a clearance TDA will be heavily
influenced by available data and the concept of the
clearance process.
• It is important to face certain issues early in
development, rather than late.
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ABOUT MOWING THE LAWN
• Why don’t we just “mow the lawn” and go home?
•Radius of effects is not definite
•Environmental variations
•Buried mines
•Mixed mines
•Inherent randomness
•Mine counters, probability actuators, sensitivity
•Distractions
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NINE ISSUES
1. What will be in the database?
2. Sweeper casualties?
3. Mixed mine types?
4. Mixed sweep types?
5. Optimization or evaluation?
6. Input estimated mine numbers?
7. Geometry rectangular?
8. Sequential clearance?
9. Is it a game?
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1. SWEEP/HUNT DATABASE
• Use A and B, where AB = area under lateral range curve
• Or use the lateral range curve itself
pd
Lateral range
• Or avoid lateral range curves, as in
SL(sweeper)-TL(environment)>DT(mine)+noise
• Or use a detailed simulation such as TMSS
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2. SWEEPER CASUALTIES
 Assume no casualties
 Tremendous conceptual simplification
 UMPM, NUCEVL, UCPLN, MEDAL,...
 Or assume casualties have only economic implications
 Replacements available immediately, at a cost
 Decouples mine types
 COGNIT, MIXER(opt)
 Or permit casualties to potentially spoil the plan
 Clearance plan only partially completed
 Mine types not decoupled
 BREAKTHRU, MIXER(sim)
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3. MIXED MINE TYPES
 Good tactics for the miner, commonly
encountered (IRAQ)
 Cheap generality if mine types are decoupled
 Clearance is mainly a search problem
 NUCEVL, UCPLN
 Potential couplings between mines
 Sweeper kills
 Sweeper inefficiencies (time delays)
 Threat to traffic (all mine types contribute)
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4. MULTIPLE SWEEP TYPES
 Order of entry important if sweepers are vulnerable
 7! = 5040 possible orders with seven sweep types
 Can multiple types sweep at the same time?
 Fratricide danger
 Helicopters usually precede ships
 Aid tactical choice of clearance type
 Sweep or hunt?
 Mechanical gear or sled?
 Remote vehicles?
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5. TACTICS OPTIMIZATION
 Tactical questions
 Track spacing
 Time on task by sweep type
 Equipment settings
 Measures of effectiveness
 Total clearance time (T)
 Clearance casualties (C)
 Target traffic casualties (H)
 MIXER (opt) minimizes C + H subject to constraint on T
 COGNIT minimizes C subject to constraints on T and H, etc.
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6. ESTIMATED MINE NUMBERS
 Number of mines may need to be an input
 Required for most optimization issues
 It is not true that SIT + clearance level = 1
 Number of mines notoriously random
 Initial guesses will be WAGs
 Need mine inventory database by country
 Updating by evidence (Bayes)
 MIXER requires mean and standard deviation by
type
 COGNIT assumes Poisson distribution
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7. GEOMETRY
Conventional rectangular (all but MEDAL)
MEDAL allows arbitrary path orientations
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8. SEQUENTIAL CLEARANCE
 Conventional method has one plan, no feedback
 Sequential method is to clear, observe, clear, …
 Clearance achieved in stages
 Plan for stage n + 1 depends on results in stage n
 Summary statistics passed from stage to stage
 MIXER optimizes within a stage, but not between
 MEDAL passes summary statistics between
stages
 COGNIT and most other clearance programs are
conventionally oriented
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9. GAME THEORY
 Minefield clearance is a competition
 Mother Nature doesn’t make minefields
 Why not use the zero-sum theory?
 Clear opposition of interest
 Mine sensitivity settings, for example,
are an enemy choice not observable by
the sweeper
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10. ADVANTAGES OF
GAME THEORY
 Lack of requirement to guess things
that cannot possibly be known, such
as mine counter settings
 Robustness of resulting tactics
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11. DISADVANTAGES
 Sensitivity to objective function
 Optimal tactics may be mixed
 “Flip a coin to decide whether to sweep
or hunt first”
 For a mine, “flip a coin to decide
whether to detonate”
 Computation is still an issue
 But computers are getting faster…
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SUMMARY
 Crucial decisions about clearance model
should be faced early in development
 Resulting software strongly affected
 Effects are interrelated
 ………………………….……..Questions?
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