Closed loop PID feedback mechanical arm. Uses a pair of hall-effect absolute encoders to determine its position, and the motion is through a Sabertooth H-Bridge and a couple brushed motors. An Arduino handles the control and feedback. Never did quite finalize the PID loops as other projects came in, but the issue is with the differing moments of inertia depending on the position of the arm. Need to write a blended PID with differing tuning parameters for the different extensions.