Bode Plot Stability Margins

Compute the gain and phase margins of a control loop from its open-loop transfer function and decide whether the closed loop is stable.

Constraints

• Function: [gm_db, pm_deg, stable] = margins(num, den).
• Gain margin in decibels, phase margin in degrees.
• Use margin on a tf object.
• Treat an infinite gain margin as stable in that respect.
• A system with no gain crossover must not error.
• Return stable as a logical.