Hi guys, This is a modified PICO. This is one of my product prototypes. You will find in our online shop in few days.
I use Arduino and 2 ir SHARP distance sensors to give stability to the robot.
Here it is the original article: 
http://www.gioblu.com/index.php?option=com_content&view=article&id=100:self-balancing-robot-per-noobs-p&catid=36:robotica&Itemid=34 
(please click on the flag of your country to get the right traduction, it uses Google translate. If the traduction is not well, it's not my fault, but of Mountainview)
I have implemented PID algorithm (it works well look @ the 3rd video) you can find my little tutorial here:
http://www.gioblu.com/index.php?option=com_content&view=article&id=102:che-cose-lalgoritmo-pid&catid=38:programmazione&Itemid=7 
 
Self balancing
Actuators / output devices: microservos 
Control method: PID 
CPU: Arduino Duemilanove 
Operating system: none 
Power source: 4x AAA 
Programming language: wiring 
Sensors / input devices: Sharp IR 
Target environment: indoor on smooth surfaces 
 
 
 
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/pico-self-balancing-robot  
             
            
               
               
               
            
            
                 
                 
              
           
          
            
            
              English is dumb 
English is dumb sometimes. The word in English is translate, not variations of traducere like in the romance languages. 
Cool robot, though; we don’t get many balancing robots here.
             
            
               
               
               
            
            
                 
                 
              
           
          
            
              
                fritsl  
                
               
               
              
                  
                    June 29, 2010,  3:17pm
                   
                   
              3 
               
             
            
              A little more info would be 
A little more info would be nice. How does it balance?
             
            
               
               
               
            
            
                 
                 
              
           
          
            
            
              Oh my god 
English is messy. I am thinking to traduce all the site in english, Google trasnlate is useless as far as babelfish.
Hi fritsl, take a look to the link.
             
            
               
               
               
            
            
                 
                 
              
           
          
            
            
              Looks like it measures the 
Looks like it measures the distance from the floor with an IR sensor, and uses PID to control how much the wheels go forwards or backwards, it’s the simplest/cheapest way to do a balancing 'bot, I’ve been meaning to make one like this but never quite did it.
             
            
               
               
               
            
            
                 
                 
              
           
          
            
            
              Nice bot, I like it! Did you 
Nice bot, I like it! Did you manage to add driving control code? I want to see it finding the exit from a maze… hehe!
             
            
               
               
               
            
            
                 
                 
              
           
          
            
            
              none 
Hi, I am working firstly on the PID algorithm look @ my state now: it is working quite well: 
http://www.youtube.com/watch?v=wMXOHRbkQsk 
What do you think about it?
 
Then It will be incredible to work on obstacle avoidance and a little of maze solving!! Have you any experience here?? I have not.
             
            
               
               
               
            
            
                 
                 
              
           
          
            
            
              maze solving is pretty 
maze solving is pretty simple, here’s a nice PDF about it from pololu:
line-maze-algorithm.pdf