A central
issue in dynamical systems and control theory is stability of equilibria.
The upper right and lower left boxes in the Nonlinear Systems Lab logo
connote phase portraits for a planar dynamical system. The upper right
phase portrait represents a saddle point (an unstable equilibrium) while
the lower left phase portrait represents a center (a stable equilibrium).
The area where the two portraits overlap suggests the rich variety of
problems that arise in nonlinear systems theory and control. For example,
the system depicted here possesses multiple equilibria, a phenomenon
which only occurs in nonlinear systems. More abstractly, viewing the
logo from the upper right to the lower left suggests stabilization,
a feedback transformation from an unstable equilibrium to a stable one.