Subsumption Architecture

In the examples this week, the robots have simple behaviour: e.g. they seek lights or avoid them depending on whether they can see a light then. In previous weeks, in the exercises, you defined what the robot should do at one moment just on the basis of its sensors at that time.

In each case there is very simple behaviour, but in practice more is needed. In the case of predator prey, if the predator is next to the food the prey wants to eat, it is probably better (unless it is very quick) for the prey to go and look for food elsewhere.

In effect, there are two forms of behaviour – get food – avoid being eaten – and the robot has to decide which is more important: one behaviour should have priority over the other.

Rodney Brook’s subsumption architecture addresses this:

• Different commands have different levels
• Higher level commands subsume lower level ones
• They may even inhibit lower level ones
• If a high level command is missing, the robot can still operate, though at a reduced capacity.

Here is an example:

Suppose a robot is to explore its environment by:

• following the lights it sees,
• avoiding loud noises and
• avoiding other obstacles.

It will have sensors for lights, noises and obstacles It will have behaviour for each of these sensors It will have an overarching ‘explore’ behaviour All of these will combine to drive the motors

Rodney Brooks is an emeritus professor renowned for his work on robotics. He is also the founder of Rethink robotics – the company that makes Baxter.