Topic: Control Systems
Consider the following statements:
A proportional plus derivative controller
(i) Has high sensitivity
(ii) Improves the steady state accuracy
(iii) Increases the stability of the system
Which of the following statements are correct?
- A. (i), (ii) and (iii)
- B. (i) and (ii)
- C. (ii) and (iii)
- D. (i) and (iii)
Answer: D. (i) and (iii)
Explanation: A Proportional-Derivative (PD) controller improves the transient response by adding phase lead, thereby increasing the system's stability margin (iii is true). Because the derivative action amplifies high-frequency noise, it makes the system highly sensitive to noise (i is true). However, a PD controller does not improve steady-state accuracy; that requires an integral (I) controller. Therefore, (ii) is false.