Nice to see development in this area.
Now I am doing much the same, except that my project incorporates the complete monitoring and control for both solar panel array as well as a micro-hydro system.
I intend also to install a tracking system on the solar array, and am digging big hole in ground as we speak for a 8 metre or for you usa folks a 4x6' triangle mast tower.
Now what i noticed with your design that did strike me with some concern is potential problems with wind loading.
With using pulleys and such, I tend to think that one good gust of wind and your belts would be snapped or slipped and your nice panel will then likely be a lovely weather cock.
I am wondering, is this something you have thought about, or is the total surface area of your panels so small that it would not e effected by such a strong gust?
I will be using a good solid ram drive, similar to what is used for satellite dish positioning, welded steel frame and suitable bearings.
Also, someone mention using a RTC as a backup, that is a good idea.
The system I am designing will not use light sensors for directional operation, but using NTP, network time protocol as my system is connected to the internet anyhow.
You have obviously spent a great deal of time making fantastic CAD drawings which makes it far easier to see and visualise your design.
Looking forward to hearing of your results.
rockwallaby