UNIT-I

1. Define open loop and closed loop system An open-loop (direct) system operates without feedback and directly generates the output in response to an input signal

A closed-loop system uses a measurement of the output signal and a comparison with the desired output to generate an error signal

2. Compare open loop and closed loop system

3. What are the components of block diagram ? The basic components of block diagram are 1. block, 2. branch point, Pick off point or take off point 3. summing point, 4. Direction of signal flow 4. Define transfer function It is the ratio between the Laplace Transform of the o/p variable to the Laplace Transform of the i/p variable with initial conditions zero 5. State Mason’s Gain formula The transfer function, C(s)/R(s), of a system represented by a signal-flow graph is; n

C ( s)  R( s)

 P i 1

i

i



Where n = number of forward paths. Pi = the i th forward-path gain. ∆ = Determinant of the system ∆i = Determinant of the ith forward path ∆ is called the signal flow graph determinant or characteristic function. Since ∆=0 is the system characteristic equation. UNIT-II 1. What are the various time domain specifications? 1.Delay time, 2.Rise time, 3.Peak time, 4.Maximum overshoot, 5.Settling time

2. How do you find the type of the system? The type number is given by number of poles of loop transfer function at the origin. 3. What is meant by peak over shoot? It is defined as the difference between the peak value of step response and the steady output.

4. What is steady state error?

5. Give expressions for static error constants

6. What are dynamic error constants? And their advantage over static error constants?

7. What are the effects of PI controller?

8. What are the effects of PD controller?

UNIT-III 1. What are frequency domain specifications?

    

Bandwidth Cutoff frequency Gain margin Phase margin Peak resonance

2. Define gain margin and Phase margin. Gain margin 

The gain margin indicates the amount of the gain which can be introduced in the system till system reaches on the verge of instability. Here positive gain margin indicates that such a gain introduction is possible till system becomes unstable i.e. system is basically stable. 

Phase margin is the amount of the lag which can be introduced till system reaches on the verge of instability so positive phase margin indicates that such a introduction possible and the system is stable. 3. What is corner frequency? Corner frequency is frequency till which the db gain of a term is neglected 4. What are M and N circles? The magnitude, M of the closed loop transfer function section with unity feedback will be in the form of circles in complex plane for each constant value of M. The family of these circles are called M circles. Let N= tanα where α is the phase of closed loop transfer function with unity feed back. For each constant of N, a circle can be drawn in the complex plane the family of these circles are called N circles. 5. What is the use of Nichola’s chart?

The chart consisting of constant-magnitude loci and constant phase-angle loci in the log-magnitude versus phase diagram is called Nichols chart. 6. What are the advantages and disadvantages of Phase lag network? 7. What are the advantages and disadvantages of Phase lead network?

UNIT IV 1. Define BIBO stability A system is defined to be BIBO Stable if every bounded input to the system results in a bounded output over the time interval

.

2. State Routh Hurwitz stability criterion.

3. State any two advantages of Hurwitz stability criterion

4. State any two limitations of Hurwitz stability criterion

5. What is root locus? It is a graphical method of plotting the locus of the roots in the s- plane the gain K is varied from 0 to infinity 6. Define Nyquist stability criterion. If the contour of open loop transfer function G(s) H(s) in G(s) H(s) plane corresponding to Nyquist contour s- plane encircles the point -1+j0 in the counterclock wise direction as many times as the number of right half s plane poles of G(s) H(s), then the closed loop system is stable.

UNIT –V 1. What are the disadvantages of Transfer function analysis?

2. Define state model of Nth order system.

3. What are the advantages of state variable analysis?

4. What are sample and hold circuits? sample and hold (S/H, also "follow-and-hold"[1]) circuit is an analog device that samples (captures, grabs) the voltage of a continuously varying analog signal and holds (locks, freezes) its value at a constant level for a specified minimum period of time.. They are typically used in analog-to-digital converters 5. What are the properties of State transition matrix?

6. Define controllability of a system

7. Define observability of a system.

PART – B UNIT-I 1. Find the transfer function X(s)/ F(s)

2. Find the transfer function

Answer

3. Give signal flow graph terminologies

UNIT-II 1. Derive expression for the response of second order system for step input for underdamped case.

2. Derive expressions for time domain specifications

UNIT-III 1. What are the frequency domainspecifications?

2. Derive M and N circles M- circles

N –Circles

UNIT-IV 1. Explain the effect of pole position on stability

2. Explin Routh –Hurwitz Criterion

3. Explain the rules of Root Locus Construction

Unit –V 1. Obtain transfer function from state model

2. Explain pulse transfer function Pluse Transfer Function Pulse transfer function relates Z-transform of the output at the sampling instants to the Z- transform of the sampled input. When the same system is subject to a sampled data or digital signal r*(t), the corresponding block diagram is given in Figure 1 .

Block diagram of a system subject to a sampled input The output of the system is C(s) = G(s)R*(s). The transfer function of the above system is difficult to manipulates because it contains a mixture of analog and digital components. Thus, for ease of manipulation, it is desirable to express the system characteristics by a transfer function that relates r*(t) to c*(t), a fictitious sampler output, as shown in Figure One can then write:

Since c(kT) is periodic,

with c(0) = 0 Similarly,

Again,

Since R*(s) is periodic R*( s + jnws ) = R*(s). Thus

If we define

, then

.

is known as pulse transfer function. Sometimes it is also referred to as the starred transfer function. If we now substitute z = eTs in the previous expression, we will directly get the z-transfer functionG(z) as