MU Instrumentation Engineering (Semester 8)
Digital Control System
December 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary


Attempt any four:
1 (a) Derive the Lyapunov equation for a system x(k+1)=Gx(k).
5 M
1 (b) State sampling theorem. Explain folding and aliasing in brief.
5 M
1 (c) Specify the region in z-plane that corresponds to the shaded region in s-plane as shown in Fig. 1

5 M
1 (d) Explain digital control system with neat block diagram.
5 M
1 (e) Explain sampler as an impulse modulator.
5 M
1 (f) Explain operation of extrapolative and interpolative FOH.
5 M

2 (a) Define pulse transfer function. Obtain C(z)/R(z) for the system shown in Fig. 2.

10 M
2 (b) Determine the stability of the system having characteristic equation
P(z)=z3-2.661z2+2.508z-0.8187=0.
using Jury's Stability criterion.
10 M

3 (a) Derive the transfer function for the ZOH.
10 M
3 (b) prove using similarity transformation that state space representation is not unique. Also prove the invariance of eigenvalues under the similarity transformation.
10 M

4 (a) Obtain the pulse transfer function for the digital control system described by \[ x(k+1) = \begin{bmatrix} 0 &1 &0 \0 &0 &1 \\-0.06 &0.07 &0.6 \end{bmatrix}x(k)+ \begin{bmatrix} 0\0 \1\end{bmatrix} u(k) \ y(k) = \begin{bmatrix} 1 &0 &0 \end{bmatrix} x(k) \]
10 M
4 (b) Represent the following system into the controllable canonical form. \[ G(z)=\dfrac {0.5z-0.25}{z^3-0.4z^2 ? 0.39z+0.126} \]
10 M

5 (a) Obtain the steady state error constants for a digital control system for step, ramp and parabolic inputs.
10 M
5 (b) Obtain the solution to the system of equation \( x(k+1) = \begin{bmatrix}0 &1 \\-0.15 & 0.8 \end{bmatrix} x(k) \). Assume initial condition x(0)=(1, 0)' and sampling time 0.5 sec.
10 M

6 (a) Design the deadbeat observer for the following system. \[ \phi (k+1) = \begin{bmatrix}0 &1 \1 &2 \end{bmatrix} \phi (k), \ y(k)=[1 \ 0] \phi (k) \]
10 M
6 (b) Write the steps for controller design via pole placement using ackermann's method.
10 M

7 (a) Explain Lyapunov stability theorems for a digital control system.
10 M
7 (b) Determine the stability of the system using lyapunov equation. \[ x(k+1) = \begin{bmatrix} 0 &1 \\-0.72 &1.8 \end{bmatrix} x(k) \]
10 M



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