http://www.robotgroup.net/mark/Centipede_concept1.gif

The Centipede is a segmented insect-like robot. The segments are constructed such that they are removable and "stackable". That is, the robot can be made almost any length you like.

I have been encountering some problems in the design definition stage. The big problem is that of knowing the turn angle. I would like to use a pot for it but all the ones I have looked at have a high friction on the wiper. The robot is light weight so this is unacceptable. If you know of a small, low-friction potentiometer, please drop me a line.

Failing that, I decided that a flex sensor (http://www.spectrasymbol.com/bend.html) would be a good choice. They only sense flexing in one direction so I would need two of them back to back. I figure they would have to be about one inch long.

I plan on using the Motorola Nitron series of HC08 microcontrollers. I am eyeing the [http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=68HC908QT2&nodeId=01624684498634 68HC908QT2] or the [http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=68HC908QT4&nodeId=01624684498634 68HC908QT4]. The difference between the parts is the size of the code space: the QT2 has about 1.5KB and the QT4 has about 4KB. The devices are based on Flash technology, have a four channel eight-bit ADC, six I/O pins (some are muxed with the ADC), are eight pin packages, and have an internal clock.

The pins are assigned thusly (assuming using flex sensors):
{{{Left motor control
Right motor control
Left turn angle sensor
Right turn angle sensor
GPI for "all stop"
Vss
Vdd
spare}}}

Assuming I can find a good potentiometer:
{{{Left motor control
Right motor control
Reverse motor control
Turn angle sensor
GPI for "all stop"
GPI for "reverse"
Vss
Vdd}}}

I am considering making the brain of the Centipede using a Cypress [http://www.cypress.com/cfuploads/img/products/CY8C26443.pdf PSoC]. I became aquainted with this part when I was at Dell and it is capable of some very complex processing. It has analog and digital blocks. As a general-purpose processor, it does not work so well, but for embedded applications, it is terrific!

=== Nuts and volts! I got screwed! ===

What do you know about that! In this month's issue (October 2003) of [http://www.nutsvolts.com Nuts and Volts] there is a centepede robot on the front cover!

No kudos to me in the article though. Parallel-divergent evolution? It could happen. Just remember where you heard it from first! ;-) Mine's cooler anyway since my design is autonomous and his RoboPede is remote controlled. Sadly, little progress has been made on mine as being unemployed prevents one from the having the funding needed for these things. When it comes down to motors and microchips versus babyfood, the babyfood wins every time.