Based on HMC E79 Practicum 5 — Underwater Robot Depth Control
The robot uses proportional control: thrust = Kp(zd - z)
This creates a 2nd-order system. Increasing Kp speeds up response but may cause oscillation.
The damping ratio ζ determines behavior: ζ < 1 oscillates, ζ = 1 is critically damped, ζ > 1 is sluggish.
Try it: Find the Kp that gives the fastest response with < 20% overshoot!