Anna University

Control System IMPORTANT QUESTIONS

(Department of ECE)

Subject Code : EC2255

Subject Name : CONTROL SYSTEMS

UNIT I

1.Using masons gain formula determine the ratio C/R for the system represented by the following diagram

2. Determine the overall transfer function of the following diagram

3. Obtain the response of unity feedback system whose open loop transfer function is G(S) =4 / {s (s + 5)} and when the input is unit step

4. Obtain the analogous electrical network for the following block diagram

UNIT II

1. A unity feedback system G(s)=10/s(s+1)(s+2).Find the steady state error when it is subjected to the i/p r(t)=1+2t+1.5t2

2. Derive an expression for the time response of an under damped second order system and when the input is unit step

3. Explain in detail the system response with PD,PI and PID Controller

4. Derive an expression for time to peak and peak overshoot for a second order under damped system

UNIT III

1. Draw the Bode plot of the G(s) = K / S(S+1)(0.1S+1) .Hence obtain the exact plot by doing necessary corrections at corner frequencies.

(i)Find the gain cross over freq, Phase cross over freq, margin and phase margin.

(ii)Find the value of K for phase margin = 20 deg.

2. The open loop transfer function of a unity feed back system is G(s) = 1 / s(1+s)(1+2s) .Sketch the polar plot and determine the gain margin and phase margin

3. Obtain the unit impulse response and the unit step response of a unity feedback system whose open loop transfer function is G(S) = (2s + 1)/ s2.

4. Determine the generalized error coefficient and steady state error for a system whose open loop transfer function is G(S) = 1/ { s (s+1)(s+10) }and the feedback transfer function is H(S) = (s+2) with input r(t) = 6 + t + t2

UNIT IV

1. Check The stability of the system

(i) .

(ii) .Determine the range of K when the system is stable

2. Sketch the root locus for the system and write about the system stability

G(s)H(s)=K(s+4)(s+5)/(S+4)(S+1), K>0

3. A feedback control system has a open loop transfer function G(s)H(S)=K/(S(S+3)(S2 +2S+2))

Find the root locus as K Varies From 0 to α

Unit V(Important Problem to go through )

1. Look Problem to Determine controllability and observability

2. Problem regarding Response to some unit step input, For data control system

3. Determine the transfer matrix for a given data

4. Problem using cascade method.