I think I will let the videos and photos speak for themselves, but to give an overview...
Walter is fully custom built, I made every part including many of the PCBs. He weights about 30kg and is powered by (2) DeWalt drill motors though chain drive. I recently milled some new sprockets and added another set of gearing dropping the overall ratio by another 3:1. I am not sure of the total gear ratio, but at one time you could ride on top and he is 3 times stronger (and slower) than that now. The sprockets were made by tracing another sprocket (with a Sharpie) and simply grinding them out by hand. A 12v 12Ah SLA battery takes care of the drive power via a Dagu Wild Thumper motor controller. This same unit charges the battery as well. 2 custom made (around the MAX713 chip) onboard charges take care of the 7.2v racing packs --one supplies data power, the other does the servos.
Brains consist of 2 Gadget Gangster Propeller boards, one being a slave to the other. The "main" chip takes care of the "personality", navigation, video for the monitor and keeps an eye on the wheel encoders. The second "slave" chip runs all the servos, runs predetermined "head routines", fires and sweeps the sonar, tracks the IR homing beacon with the WiiCamera and also runs the WiiCamera/Laser Lidar system. The multi-cog prop system makes chip to chip communication a breeze. Each chip has a dedicated cog that does nothing but serial watching and updates variables as new data comes in. All the other cogs have access to these variables so for example, the main navigation loop never stops to go and fire off the sonar, instead the sonar is constantly being fired in the background and variables are constantly being updated. When the navigation loop needs sonar data, it already has it. It always has it. And it always has the most recent numbers. Everything is super-duper global and with the chips talking at 115,200, it is like they are one single chip. Everything is in the background, set it and forget it.
BlinkM's take care of the eyes, and a MP3 player takes care of the voice. Walter uses many different voices and sound effects, the main 2 voices being A) text to speech I dub from online and B) a good buddy of my in London who records lines for me and emails them. So far, he has recorded over 200 words and phrases for Walter. I try to send him "batches" of lines to do so until I have a "batch" big enough to send, the text-to-speech voice is used. There is also a speech recognition system onboard as well but I just can't seem to find the time to do anything with it. Soon.
Overall, Walter is the sum of about 2 1/2 years work, a couple/few thousand dollars (all spent in nickles and dimes) and a lot of lost hair. I would say he is about 1/2 way to where I would like him to be.
**NOTE** I have also finished Walter's new transmitter and it can be found at http://letsmakerobots.com/node/27251.
Just a Stroll Outside
Photos: (All photos are clicky-make-them-bigger)