Amity University 2007 B.E Electrical and Electronics Engineering CONTROL SYSTEMS 2 KS WITH ANSWERS - Question Paper

1. What is frequency response ?
The frequency response is a steady-state output of the system, when the input is a sinusoidal signal.
---------------------------------------------------------------------------------------------------
2. What are advantages of frequency response analysis ?
1. The absolute and relative stability of the closed loop system can be estimated from the knowledge of the open loop frequency response.
2. The practical testing of system can be easily carried with available sinusoidal signal generators and precise measurement equipments.
3. The transfer function of complicated functions can be determined experimentally by frequency response tests.
4. The design and parameter adjustment can be carried more easily.
5. The corrective measure for noise disturbance and parameter variation can be easily carried.
6. It can be extended to certain non-linear systems.
---------------------------------------------------------------------------------------------------
7. What are frequency domain specifications?
Fhe frequency domain specifications shows the performance of the system in requency domain, and they are
1. Resonant peak 4. Cut-off rate
2. Resonant frequency 5. Gain margin
3. Bandwidth 6. Phase margin.
---------------------------------------------------------------------------------------------------
8. Define Resonant Peak ?
The maximum value of the magnitude of closed loop transfer function is called Resonant Peak.
---------------------------------------------------------------------------------------------------
9. What is Resonant frequency ?
Tie frequency at which the resonant peak occurs is called Resonant frequency. The resonant peak is the maximum value of the magnitude of closed loop transfer function.
---------------------------------------------------------------------------------------------------
10. Define Bandwidth ?
The Bandwidth is the range of frequencies for which the system gain is more lan -3db.
---------------------------------------------------------------------------------------------------
11. What is cut-off rate ?
The slope of the log-magnitude curve near the cut-off frequency is called cut-Off rate.
---------------------------------------------------------------------------------------------------
12. Define gain margin ?
The gain margin, Kg is described as the reciprocal of the magnitude of open loop transfer function, at phase cross-over frequency, ?pc.

Gain margin, Kg = 1¬¬¬¬____
| G(j?) | ?=?pc

When expressed in decibels, it is provided by, the negative of db magnitude of G(jco) at phase cross-over frequency.
Gain margin in db = 20 log 1¬¬¬¬____ = -20 log | G(j?) | ?=?pc

| G(j?) | ?=?pc

---------------------------------------------------------------------------------------------------

Earning:   Approval pending.