IMHO, the main design flaw for Tri-bot is the position of his IR obstacle avoidance sensors. Although he has a pair of IR emitters, his IR receiving sensors are a foot above ground, preventing him from seeing any obstacle below his chest level, and thus grinding his wheels and gears when stopped by something that is below 20 cm from the ground, which is most obstacles other than walls or people.
I have not seen a single post that deals with this, and just a few complaints. MrScott recommended in 2009. to add extra sensors in parallel to original ones, but neither he or anyone else reported that as working. My idea would be to relocate one of the sensors 20 cm lower from where they are originaly (i.e. at 10 cm or less from the ground), so I am wondering if anyone tried it and was successful?