Q8Control System
Question
Q.8. What is dominant pole?
Answer
A dominant pole is the closed-loop pole (or complex-conjugate pole pair) closest to the imaginary axis, whose contribution decays slowest and therefore dominates the overall transient response, allowing a higher-order system to be approximated by a lower-order (often second-order) model.
In a system with multiple closed-loop poles, the dominant pole(s) are those located nearest to the jω-axis (i.e., having the smallest real-part magnitude) compared to the other poles, which are typically located much farther to the left (at least 5 times the real part of the dominant pole, by common rule of thumb). Because the transient response terms associated with far-left poles decay much faster (e^(-large·t)) than those from the dominant pole(s), the dominant pole's exponential/oscillatory term persists longest and effectively governs the overall shape, settling time, and overshoot of the system response, permitting an accurate approximation of a high-order system by a simpler first- or second-order model based on the dominant pole(s) alone.