Penelope by Riccardo Rocca

Penelope is a small robot 25 cm high and 20 cm in diameter.
I had built it in order to take part to a national microrobot competition which was held in Pisa (Italy), in April 93.
Its aim is to move autonomously, looking for light, sound and gas
sources, without hitting obstacles.

It is provided with:
 - 5 sonars and 6 whiskers for obstacle avoidance
 - 5 groups of directional light sensor, 3 directional microphones
   with 4kHz filters and one gas sensor for sources searching
 - one compass and one odometer (=mileometer) for positioning
 - two DC motors for moving
 - one 12V lead battery for power supply
 - one Motorola micro-controller M68HC11, mounted on the Motorola
   Evaluation Board (EVB) that provides the user with:
   - one 8KB EPROM
   - one 8KB RAM
   - connection to a PC serial port for debugging

In order to check the numerous sensors and devices of Penelope I also developed a program in BASIC that communicates with the robot via the PC serial port.
In this way the robot can be driven with the arrow keys of the PC keyboard, while the response of all sensors is displayed on the PC screen.

I planned and built Penelope in 12 months of hard job.
It costed around 600 US$, half of which was due to the purchase of the M68HC11 evaluation kit.

The main problem that I had to solve was about the software, namely which strategy should the robot follow in order to quickly find the largest number of sources.
In the beginning I had decided to provide the robot with compass and odometer, because I was planning to let the robot keep a track of its mouvements and memorize a map of the places already visited, so as to avoid to track the same source twice.
But during the test phase I soon discovered that any attempt to give the robot an intelligent behaviour was only slowing down its speed. Finally I opted for a much more instinctive behaviour, where the robot would simply move around as quickly as possible, in order to explore the competition field as much as possible, thus increasing the chance to find out new sources.
Consequently I had to spend most of my efforts in developing the accuracy of the robot's sensors (especially the ultrasounds), rather than the robot "intelligence".

Informations about Penelope and about two other robots, that I had built earlier, are available at URL:

There you can also find a suitable picture of Penelope.
The site will be further developed, also by adding more pictures and the electronic schemes.


  Riccardo Rocca


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