Question

A proportional integral (PI) controller results in which of the following ? 
1. Improves the transient response without affecting steady state response
2. Improves the steady state response without affecting transient response
3. Improves both transient response and steady state response
4. Improves the steady state response while marginally affecting transient response, for well designed control parameters

Answer 1

Correct Answer - Option 4 : Improves the steady state response while marginally affecting transient response, for well designed control parameters

PI Controller improves the steady state error due to integral action but proportional action improves the transient response marginally by speeding up the transients.

Effects of Proportional Integral (PI) controllers:

• Increases the type of the system by one
• Rise time and settling time increases and Bandwidth decreases
• The speed of response decreased i.e. transient response becomes slower
• Decreases the steady-state error and steady-state response is improved
• Decreases the stability

Effects of Proportional Derivative (PD) controllers:

• Decreases the type of the system by one
• Reduces the rise time and settling time
• Rise time and settling time decreases and Bandwidth increases
• The speed of response is increased i.e. transient response is improved
• Improves gain margin, phase margin, and resonant peak
• Increases the input noise
• Improves the stability