(SEM V) THEORY EXAMINATION 2017-18 CONTROL SYSTEM-I

CONTROL SYSTEM-I (NIC-501)

B.Tech | Semester V | Section-wise Important Questions & Notes

SECTION A – Very Short Answer (2 × 10 = 20 Marks)

This section checks definitions, basic concepts, and key terms. Answers must be precise and formula-oriented.

Important Questions

Define transfer function.                                             What is a non-touching loop?

Define gain crossover frequency and phase crossover frequency.

What is corner frequency and bandwidth?                What is steady-state response?

List time-domain specifications.                                 Write the condition for controllability of a system.

What is an asymptote (root locus)?                              State the necessary condition for stability.

Define dominant pole and impulse response.

Key Notes

Transfer function = Output/Input in Laplace domain (zero initial conditions).

Gain crossover frequency (ωgc): |G(jω)| = 1.

Phase crossover frequency (ωpc): Phase = −180°.

Time-domain specs: Rise time, peak time, settling time, overshoot.

Dominant poles decide system speed and damping.

SECTION B – Long Theory & Numericals (Attempt Any 3)

This section is very important and includes derivations, plots, and numericals.

Important Questions

Determine the transfer function of a given block diagram system.

Derive the step response of a first-order system and draw its response.

Plot the Bode diagram for

1. G(s)=Ks2(1+0.2s)(1+0.02s)G(s)=\frac{K s^2}{(1+0.2s)(1+0.02s)}G(s)=(1+0.2s)(1+0.02s)Ks2​

and find gain & phase crossover frequencies.

Sketch the root locus for

1. G(s)=Ks(s+2)(s+4)G(s)=\frac{K}{s(s+2)(s+4)}G(s)=s(s+2)(s+4)K​

and find K for damping ratio ζ = 0.5.

For a unity feedback system, find error constants and steady-state error.

Key Notes

First-order system has no overshoot.

Root locus questions are high-scoring if steps are shown.

Error constants:

Position: Kp

Velocity: Kv

Acceleration: Ka

SECTION C – Signal Flow Graph (10 Marks)

 Important Questions

Find overall gain using Mason’s Gain Formula from a given signal flow graph.

Draw a signal flow graph from a block diagram and evaluate closed-loop transfer function.

Key Notes

Mason’s formula is frequently repeated.

Identify forward paths, loops, non-touching loops clearly.