Topic: Control Systems
Consider a closed loop stable phase locked loop system having an open loop transfer function $G(s) = K(K_1 + K_2/s)(1/s)$. The system is capable of producing zero steady state error E(t) for
- A. Phase step only
- B. Constant velocity and phase step
- C. Acceleration
- D. Jerk
Answer: B. Constant velocity and phase step
Explanation: The open-loop transfer function is $G(s) = \frac{K(K_2 + sK_1)}{s²}$, which indicates two poles at the origin (Type 2 system). A Type 2 system produces zero steady-state error for step inputs (phase step) and ramp inputs (constant velocity). It produces a finite steady-state error for parabolic inputs (acceleration).