Question

Which of the following is NOT the disadvantage of lag compensator in a control system?
1. In lag compensator, the attenuation offered by it shifts the gain crossover frequency to a lower point, thereby decreasing the bandwidth.
2. The lag network offers a reduction in bandwidth, and this gives shorter rise time and settling time and so the transient response.
3. A lag compensator somewhat acts as a proportional plus integral controller, hence adversely affects the stability of the system.
4. Though the system response is longer due to decreased bandwidth, the response is quite slow

Answer 1

Correct Answer - Option 2 : The lag network offers a reduction in bandwidth, and this gives shorter rise time and settling time and so the transient response.

Advantages of Lag Compensator:

• A phase lag network offers high gain at low frequency. Thus, it performs the function of a low pass filter.
• The introduction of this network increases the steady-state performance of the system.
• The lag network offers a reduction in bandwidth and this provides longer rise time and settling time and so the transient response.
• The angular contribution of the pole is more than that of the compensator zero because the pole dominates the zero in the lag compensator.
   

Advantages of Lead Compensator:

• It improves the damping of the overall system.
• The enhanced damping of the system supports less overshoot along with less rise time and settling time. Therefore, the transient response gets improved.
• The addition of a lead network improves the phase margin.
• A system with a lead network provides a quick response as it increases bandwidth thereby providing a faster response.
• Lead networks do not disturb the steady-state error of the system.
• It maximizes the velocity constant of the system.