Nemesys is a research project by the Department of Aerospace Engineering of Politecnico di Milano. The name is the acronym of Neural Ento-MEchanic SYStem, that is a machine inspired by the structure of the insects, controlled with the aid of a neural network.

The aim of the proect as a matter of fact is the making of a six-legged robot ("hexapod") for the exploration of celestial bodies, like the Moon or Mars. The shape of the robot just reminds the one of an insect.

Each of the six legs owns three degrees of freedom, in order to allow a wide movement capability; the joints are acted through eighteen brush electric engines, commanded with a PWM (Pulse Width Modulation) signal.

The engine drive is performed by six PIC microcontrollers, which can emit three PWM signals each.

Such microcontrollers can also acquire the analog signal emitted by the potentiometers which measure the position of the legs.

By the means of a digital acquisition card, the PIC communicate with a PC which sends the coordinated signals for controlling the robot.

The command signal for the microcontrollers is generated by a neural network of the CTRNN type (Continuous Time Recurrent Neural Network).

The network is trained with genetic algorithms. Further improvements of the project consider the use of spiking neural networks and non-supervised learning tecniques.

The prototype is now complete, its structure is made of aluminium, and all the necessary circuits are on board.

The robot weighs about 7.5 kg; most of the weight is due to the engines and their reducers.

In the future the robot will be made totally autonomous, with its own CPU and power source (solar panels and/or bateries).

Nemesys is a project which concerns many disciplines, among which:

• mechanichs
• electronics
• automated control
• ASM microcontroller programming
• real time programming
• neural networks
• genetic algorithms
• vision algorithms
• high-level behavioural algorithm