Hi Nathan

Sorry to disappoint you, but those panels are not laser cutted

I cutted them manually with a saw. It looks like they come out rather regular, but it's not that hard with regular rectangles.

About the buildup of speed: i implemented a

PID controller, that is a kind of algorithm that is used for reaching a desired value in a controlled system like our.

I don't know if you already know it. In few words, it's a well know way to take into account three different parameters into the calculation of the final speed: the Proportional (that is the error, in our case, the current angle of the robot), the Derivative (that is, the angular velocity, or how fast it is falling/raising), and the Integrative, which is a sum of the errors in all previous iterations.

Well, the integrative is what avoids the buildup. It is a sum of all errors (that is, currentAngle - desiredAngle) from the beginning when you start the robot. Of course it should average to zero in the long term, bug as the robot keeps going in one direction as you say, the value increase costantly and so the "corrective" action (the value of I) increase until it stops the robot from "drifting".

The problem is finding right values for the three coefficients (P, I, D), that is why i have three potentiometers in the robot. The wikipedia article has some more info. Looks like hard math but in reality is quite simple, i never heard of it befor starting this project. In the code you can easily spot the section where it is implemented.

About the backlash, yeah, i think it kills the stability. The problem is that when the baricenter passes from one side to the other, the axle goes from one end of the backlash to the other (which i think could be about 3°, very approximatively). This is expecially visible when the robot is near the stability point, as the balance quickly shifts from forward to backward. You can almost feel the "click".

I think i should change the whole train.. But that's much money!

I can't see that video, it requires some plugin that doesn't work.. is there a youtube (or similar) version? i'm interested in taking a look

thanks for the feedback