L11 - Swarm Intelligence: Flocking Behaviour

Question 1

Define what is meant by swam behaviour?

Answer 1

Behaviour which individuals of the swarm can’t perform or at least can’t perform optimally. But as a group, the behaviour can be performed.

Question 2

Explain the Slime-Mold example of swarm behaviour…

Answer 2

An amoeba that is attracted to and eats matter, but can’t scavenge effectively on its own. If it can’t find food, it splits and duplicates into a collective being (Swarm) that can find food more effectively.

Question 3

What are some of the types of collective movements?

Answer 3

1. Flocking / Shoaling
2. Swarms
3. Formation travelling

Question 4

Define Natural Movements and Artificial Movements…

Answer 4

Natural -> 2D and 3D movements that represent the natural world.

Artificial -> 1D movement ( can only move forward and backward ). E.g a train.

Question 5

What is emergent behaviour?

Answer 5

One of the main properties of flocking in which the movement of the flock naturally converges to be one.

Question 6

What is Multi-Agent Movements? If it flocking?

Answer 6

A scenario in which many agents are moving similarly, but are not necessarily flocking. For example robots moving in a pre-defined route.

Question 7

Give the characteristics of flocking…

Answer 7

1. No leader
2. Dynamic movement as a flock
3. Reactive to predators and obstacles
4. No collision between flock members
5. Tolerant of movement within flocks

Question 8

What are the 2 ways a flock might react to predators?

Answer 8

Flash Expansion -> Swarm disperses in different directions.

Fountain Effect -> Swarms splits and travels around the predator.

Question 9

Give some benefits of flocking…

Answer 9

1. Increase speed
2. Increase range
3. Reduce turbulence for back of flock.
4. Can confuse predators

Question 10

Groups migration reduces directional error of the flock. For a flock of N birds, what is the formula to calculate the flock error?

Answer 10

1 / sqrt(N)

Question 11

What is a Boid? What are it’s properties?

Answer 11

A digital representation of a member of a flock.

• Has direction
• Local awareness -> Only interested in an actions of neighbouring boids.
• Blind spot -> All have a blind spot to represent real animals.
• Identical -> All boids are identical.

Question 12

Who created Boids? What was the motivation?

Answer 12

Craig Reynolds ( 1987 )

A way to digitally simulate flocking in a computationally cheap way.

Question 13

What were Reynolds rules for flocking?

Answer 13

Separation -> Steer boids to avoid neighbours

Alignment -> Steer towards average heading of flock mates.

Cohesion -> Steer towards average position of flock mates.

Question 14

What are the characteristics of Reynolds Flock?

Answer 14

• Synchronise direction changes
• Flocks merge if they meet
• Flash expansion occurs if flocks start together
• If started too far apart, multiple flocks occur which will slowly converge into one