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Neurons, light seekers and phobes

What are neurons, light seekers and phobes? In this article, Professor Richard Mitchell explains more.
Four small light-seeking robots
© University of Reading

So let’s explain how we can have light seekers and phobes controlled by neurons.

Neurons are simple processing elements – human brains are made up of billions of them. Neurons are connected together – in what is sometimes known as a neural network. The connections between neurons are either inhibitory (which means something is less likely to happen) or excitatory (when something is more likely to happen).

For the Braitenberg vehicle:

  • An excitatory neuron tends to make a motor go faster

  • An inhibitory neuron tends to slow a motor

The light sensors determine whether a neuron is excitatory or inhibitory.

Light seeking vehicle

The two sensors have excitatory connections to opposite motors.

If the left sensor detects light but the right does not the right motor speeds up/left motor slows down. So the robot steers to the left towards light seen by the left sensor.

Similarly if the right sensor sees light, the robot will steer towards it. It will be considered an ‘Aggressive light seeker’ as it moves towards light it sees.

Alternative

Now there is a neuron making the motors go forward, but the sensors are connected inhibitorily to the motors on their side. If the left sensor detects light but the right side does not, the left motor slows down and the right continues forward. The robot steers to the left towards the light seen by the left sensor.

Similarly if the right sensor sees light, the robot will steer towards it. It will be considered a ‘Shy light seeker’ as its reaction is to make the associated wheel slow down on detecting the light.

Light phobe

A light phobe is a robot which avoids light and steers away. Connections can be made for ‘aggressive’ light phobe behaviour.

As for shy light phobe behaviour – How would you do these?

© University of Reading
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