1

MINEFIELD MODELING ISSUES

MINWARA 6

9-13 May 2004

Alan Washburn

Naval Postgraduate School

Operations Research Department

(831) 656-3127

awashburn@nps.navy.edu

2

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.

3

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

4

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?

5

1. SWEEP/HUNT DATABASE

pd

Lateral range

•Use A and B, where AB = area under lateral range curve

•Or use the lateral range curve itself

•Or avoid lateral range curves, as inSL(sweeper)-TL(environment)>DT(mine)+noise

•Or use a detailed simulation such as TMSS

6

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)

7

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)

8

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?

9

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.

10

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

11

7. GEOMETRY

Conventional rectangular (all but MEDAL)

MEDAL allows arbitrary path orientations

12

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

13

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

14

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

15

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…

16

SUMMARY

Crucial decisions about clearance model should be faced early in development

Resulting software strongly affected Effects are interrelated ………………………….……..Questions?