CL poles (×): eigenvalues of A−BK — where the closed-loop dynamics live. All must be in LHP for stability. Real part = decay speed, imaginary part = oscillation frequency.
OL poles (×): the motor's natural dynamics — fixed for a given motor (one at s=0 from the mechanical integrator, plus electrical/mechanical poles).
Ctr zeros (○): LQR doesn't produce zeros naturally. These are derived by asking: if this LQI controller were an equivalent compensator C(s) from error to control, what zeros would it have? They show whether the controller acts more like PD (real-axis zeros), PI (single zero), or has complex zeros — the bridge between Q/R weights and classical intuition.