Find an equilibrium point for a single water tank with inflow and outflow:
Linearize a model around an equilibrium point:
Linearize around an equilibrium point and analyze the stability:
Design a PI controller for keeping the level in a tank with inflow and outflow constant:
Find the equilibrium where the level

is constrained to be

:
Linearize and close the loop around a PI controller:
Show the closed-loop step response for a family of PI controllers:
Simple pendulum swinging through any angle:
Equilibrium with the pendulum hanging straight down:
Pendulum standing straight up above its axis:
Level curves of the first integral give the potential energy of the system:
The pendulum has one stable and two unstable equilibrium points: