相位裕度计算器 — 公式

Phase Margin

Phase margin is the additional phase lag that would bring the system to the verge of instability. It is measured at the gain crossover frequency (where the open-loop gain equals 1).

Approximation for Second-Order Systems

For a standard second-order system, the phase margin can be approximated from the damping ratio. A useful rule of thumb is PM ≈ 100 × zeta (in degrees) for zeta between 0.1 and 0.7.

Adequate phase margin (typically 30-60°) ensures robustness against modeling errors and parameter variations.