Skip to 0 minutes and 13 secondsAll right. We have here a number of the lab robots. They've effectively been programmed to say that, if they can't see anything, they should go forward, but if they do see something, they should follow it. And if they get too close, they can reverse away. And if you have that sort of behaviour, as you can see, you can have them following each other, to a certain extent.

Skip to 0 minutes and 46 secondsThese particular robots don't have speed control, so they are going at various speeds, which can upset the behaviour.

Skip to 0 minutes and 56 secondsIt's a bit like if you've got a mother duck leading her ducklings across a road. You see them following, and you get something like that behaviour with these robots.

Flocking and Boids

Another example of co-operative behaviour is flocking - where ‘animals’ move around in formation.

Sheep provide a good example of this in nature - one leader, the rest follow. Zebras also stay together - makes them safer: it’s difficult for a predator to distinguish one zebra from the rest.

Fish swim together in schools. Birds provide another excellent example; geese for instance, fly in a v-formation. The one’s behind are in ‘slip stream’, and use less energy.

On motorways, lorries drive behind each other in convoy - again to use less fuel.

Basic behaviour

In this video demonstration a group of lab robots have been programmed to demonstrate simple flocking behaviour, using some of the rules you’ve already met.

  • The lead ‘animal’ operates in ‘avoid obstacle’ mode.
  • The others operate in ‘follow’ mode.

Watch as the robots gather behind the leader, like a convoy of ducklings lining up to follow their mother across a road.

Craig Reynolds’ boids

Craig Reynolds is a software engineer, based in California. His research centres around using computer programs to simulate complex natural phenomenon. Reynolds writes software which simulates various types of human and animal behaviour. He has developed three rules for flocking behaviour of ‘boids’ that combined, give a realistic impression of flocking birds:

Separation Steer to avoid crowding with local flock mates.

Alignment Steer toward the average heading of local flock mates.

Cohesion Steer to move toward average position of local flock mates.

You can watch a video of the boids. At first glance, you might think you are watching birds, however on a closer inspection you will see they are artificial. Chris Langton, a pioneer in Artificial Life, explains it well:

“Boids are not birds; they are not even remotely like birds; they have no cohesive physical structure, but rather exist as information structures - processes with a computer. But - and this is the critical ‘but’ - at the level of behaviours, flocking boids and flocking birds are two instances of the same phenomenon: flocking. So these boids are examples of artificial life, ‘but not as we know it.”

What did you think of the flocking and the boids videos? Share your thoughts in the discussion and remember, you can ‘like’ comments made by others.

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This video is from the free online course:

Begin Robotics

University of Reading