Tell us about yourself!
I wasn't talking about the angle between 'a' and 's'. The math shown does not account for the fact that the further that 's' is out of the plane of rotation of the servo arm the smaller the change is in 'l' for a given change in servo angle. In the extreme, if 's' is perpendicular to the plane of servo rotation (parallel to the servo axis) 'l' does not change at all for a change in servo angle. Do you see what I'm saying now? It seems to me that there would be significant binding and error in positioning at the extremes of travel and rotation of the moving plate.
How did you compensate for the error in l generated per radian of rotation when the servo axis is not perpendicular to S? Would it be better to design a system where either the connecting rod was always in the same plane as the servo arm or beef up the math to calculate this angular error? I suppose the longer the connecting rods are the less this is a problem, but it would be a problem in a more squat system, no?