Today, we found out why the hexbot's legs oscillate when it's sitting still.
Servos convert the PWM input into a desired angle. One advantage of digital servos over analog ones is that they always correct toward the desired angle with full power, rather than proportional. They aren't weaker when correcting for small angles.
So when our hexbot is sitting still, bumping a leg even slightly from its position will induce a full-power burst of correction until the servo is again at the correct position. Since we have relatively heavy legs on low-friction bearings, the leg's momentum carries it past the zero point, and the servo corrects full-power in the opposite direction, inducing oscillation.
Servos convert the PWM input into a desired angle. One advantage of digital servos over analog ones is that they always correct toward the desired angle with full power, rather than proportional. They aren't weaker when correcting for small angles.
So when our hexbot is sitting still, bumping a leg even slightly from its position will induce a full-power burst of correction until the servo is again at the correct position. Since we have relatively heavy legs on low-friction bearings, the leg's momentum carries it past the zero point, and the servo corrects full-power in the opposite direction, inducing oscillation.