Anna University Coimbatore 2008 B.E Electrical and Electronics Engineering Control system QB - Question Paper

17. What is the basis for framing the rules of block diagram reduction technique?
The rules for block diagram reduction technique are framed such that any modification made on the diagram does not alter the input output relation.
18. What is a signal flow graph?
A signal flow graph is a diagram that represents a set of simultaneous algebraic equations. By taking L. T the time domain differential equations governing a control system can be transferred to a set of algebraic equations in s-domain.
19. What is transmittance?
The transmittance is the gain acquired by the signal when it travels from 1 node to a different node in signal flow graph.
20. What is sink and source?
Source is the input node in the signal for graph and it has only outgoing branches. Sink is an output node in the signal flow graph and it has only incoming branches.
21. Define non touching loop.
The loops are stated to be no touching if they do not have common nodes.
22. Write Masons Gain formula.
Masons Gain formula states that the overall gain of the system is
T = one S Pk ?k
? k
k- Forward path in the signal flow graph
Pk- Forward path gain of kth forward path
? = 1-[sum of individual loop gains ] +[sum of gain products of all possible combinations of 2 non touching loops]-[sum of gain products of all possible combinations of 3 non touching loops]+…
?k = ? for that part of the graph which is not touching kth forward path.
23. What is servomechanism?
The servomechanism is a feedback control system, in which the output is mechanical position (or time derivatives of position velocity and acceleration).
24. What is stepper motor?
A stepper motor is a device which transforms electrical pulses into equal increments of rotary shaft motion called steps.
25. What is servomotor?
The motors used in automatic control systems or in servomechanism are called servomotors. They are used to convert electrical signal into angular motion.
26. What is synchro?
A synchro is a device used to convert an angular motion to an electrical signal or vice versa.

27. Name the test signals used in control system
The commonly used test input signals in control system are impulse, step, ramp, acceleration and sinusoidal signals.
28. What is step signal?
The step signal is a signal whose value modifications from zero to A at t= 0 and remains constant at A for t>0.
29. What is ramp signal?
The ramp signal is a signal whose value increases linearly with time from an initial value of zero at t=0. The ramp signal resembles a constant velocity.

Earning:   Approval pending.