Topic: Control Systems
Consider the Bode plots (magnitude and phase) of two different open loop transfer functions of two unity feedback systems. The open loop transfer functions have poles in right half plane. The closed loop system formed from these open loop systems. Which of the following holds true?
- A. Closed loop system with I is stable and with II is unstable
- B. Closed loop systems using I and II both are unstable
- C. Closed loop system with I is unstable and II is stable
- D. Closed loop system with I and II are stable
Answer: A. Closed loop system with I is stable and with II is unstable
Explanation: For system I, both the Gain Margin (GM = 4 dB) and Phase Margin (PM = $20^\circ$) are positive, indicating a stable system. For system II, both the Gain Margin (GM = -4 dB) and Phase Margin (PM = $-20^\circ$) are negative, indicating an unstable system. Therefore, system I is stable and system II is unstable.