About this previous year paper
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
- 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
- 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.