by the way sorry if I have mistakes in English, I'm not a native speaker in it

1. With the system turned off, I try to balance it with hand to find where is max. stability physically, without going to equations,

2. I'd then try to adjust output of accelerometer so that final output of gyroscope and accelerometer are zero, near the point I found, well not that exact, but close to

3. The error from here is defined as: angle_set_point - filtered_angle, or just (0 - filtered_angle)

4. I use PID to get a motor output proportional to this output

Well I wish to go through the theory, starting from free body diagram and I gathered papers to read on it. In that case I'd go this way:

1. analysis of free body diagram and writing mech. equations (deepest respect for The Great Newton)

2. modeling close to my system under matlab

3. ending in working code

4. implementing physical system close to results of 1-3

With my configuration of life I'd need a 6 to 8 months to finish that, counting on my not-bad basis in math, but to take it I really need some feeling of 'close success' out of this trial and error :-)

May be there is any chance that I can get it at least swinging close to balance point (angle_set_point=0)?

Please help..