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Bio-AI > Lecture 8 - Swarms > Flashcards

Lecture 8 - Swarms Flashcards

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Biology 101 flashcards
1
Q

What is swarm engineering?

A

Engineering the collective behaviour of a group of agents for a desired purpose

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2
Q

What are 3 positives of swarm engineering?

A
  1. Robust/Flexible
  2. Scalable (though difficult in practice)
  3. More capable than sum of parts
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3
Q

What are 5 properties of individual agents in a swarm?

A
  1. Relatively homogeneous
  2. Relatively incapable (as a single agent)
  3. Simple rules define actions
  4. Interact locally only
  5. Little/no memory
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4
Q

Name 2 ways agents interact locally.

A
  1. Direct communication (wifi etc)

2. Stigmergy (communication through environment)

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5
Q

What are the two main challenges of swarm intelligence?

A
  1. Finding local rules that produce desired behaviour

2. Proving your system works

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6
Q

What are 4 methods of developing local rules for swarm intelligence?

A
  1. Trial and error
  2. Crowd source (which is essentially trial and error scaled up)
  3. Bio-inspired
  4. Artificial Evolution/Machine Learning
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7
Q

What are the 3 main rules of Flocking (Reynolds 1987)?

A
  1. Separation: maintain given distance between each neighbour
  2. Cohesion: move toward the centre of mass of neighbours
  3. Alignment: align angle agent agent faces with neighbours
    (4) /(5): Attractors (Migrator), Repulsor (Object avoidance) - not on slides, said in lecture.
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8
Q

What are the 3 basic rules/behaviours of PSO (particle swarm optimisation)?

A
  1. Brave: Explore new areas to find better food sources
  2. Conservative: Fly back to previous best food source
  3. Swarm: Move to best local area (from neighbours)
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9
Q

What is particle swarm optimisation?

A

Finding the best ‘food source’ in an area. Optimisation using a swarm to find the highest value target.

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10
Q

What are the properties of agents in PSO?

A

Can ‘shout’ the value of the food source at their current location to their neighbours
Can remember the location of the best food source it has encountered

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11
Q

How are the actions of a PSO agent governed?

A

v(t+1) = av(t) + bR(pbest-S(t)) + cR*(gbest-S(t))

v(t): current velocity
a,b,c: learning rates
R: random number [0,1]
pbest: best position already encountered
gbest: best position from neighbours 'shouts'
s(t): current position
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12
Q

What is the main use of ant colony optimisation (ACO)?

A

Find the shortest path between two nodes in a network

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13
Q

What is the main advantage of ACO over traditional searching algorithms?

A

Can work in dynamic networks. Traditional search algorithms assume the network is static.

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14
Q

What is a disadvantage of ACO?

A

Not guaranteed to find the optimal solution in networks >30 nodes

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15
Q

What is the basic ACO algorithm?

A
  1. At each node generate a random number
  2. -If rand is less than a threshold value q0: use the transition rule to pick the next path
    - If rand is greater than q0: choose the path with the highest pheromone level
  3. Go along chosen path (edge) to next node. Lay pheromone at same time
  4. Repeat
    Note: (pheromones decay over time)
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16
Q

What is the global update for ACO?

A

Once the shortest path has been found, this path is updated to have pheromones increased so inversely proportional to length.

17
Q

What are the two rules for environmental monitoring robots (to follow odor)?

A
  1. If lost: spin until you locate the plume from the odor

2. If following odor: ‘run & tumble’ until you reach the source

18
Q

What are some examples of robot swarm demonstrations?

A

Chaining: using chains of coloured robots to map a path
Coordinated box pushing: (self explanatory)
Blind bulldozing: constructing a ‘nest’ using bulldozers with only local rules
Cooperative manipulation: using pairs of robots to pick up sticks that are too heavy for an individual
Making shapes: Kilobots

19
Q

What are the 2 rules for clustering (objects)?

A
  1. Probability to pick up object: inversely proportional to N (N = number of objects seen in short time window)
  2. Probability to put down object: directly proportional to N
20
Q

Give an example of physical cooperation in swarms.

A

Ants using their bodies to:

  • build bridges
  • cover potholes
  • create nests
21
Q

What is a reconfigurable robot?

A

A modular robot that can be reorganised to create a morphology suitable for different tasks

22
Q

Give 4 examples of structural layouts for reconfigurable robots

A
  1. Lattice
  2. Chain
  3. Mobile
  4. Magnetic
23
Q

What type of communication is used in clustering?

A

Stigmergic

24
Q

What type of communication is used by Kiva Systems (Warehouse organisers)?

A

Global. An example of a ‘swarm’ which is better controlled using global over local communication

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