Suppose that the gain, time constant and dead time of a process with the following transfer function: Gc(s) = 10 exp( – 0.1s)/(0.5s + 1) are known with a possible error of ± 20% of their values. The largest permissible gain Kc of a proportional controller needs to be calculated below taking the values of process gain, time constant and dead time as________________?

Related Mcqs:

1. In a closed loop system, the process to be controlled is an integrating process with transfer function 1/2s. The controller proposed to be used in an integral controller with transfer function 1/T1s. When a step change in set point is applied to such a closed loop system, the controlled variable will exhibit__________________?

   A. Overdamped response
   B. Underdamped response
   C. Undamped response
   D. Unstable response

2. Find the ultimate gain and frequency for a proportional controller in the case of a process having the transfer function Gp(s) = 1/(4s + 1)(2s + 1)(s + 1) ?

   A. w = 1/√14, Kc = 45/7 √14
   B. w = √(7/6), Kc = 46/3
   C. w = 1, Kc = 13
   D. w = √(7/8), Kc = 45/4

3. A proportional controller with a gain of Kc is used to control a first order process. The offset will increase, if________________?

   A. Kc is reduced
   B. Kc is increased
   C. Integral control action is introduced
   D. Derivative control action is introduced

4. The offset introduced by proportional controller with gain Kc in response of first order system can be reduced by ____________________?

   A. Reducing value of Kc
   B. Introducing integral control
   C. Introducing derivative control
   D. None of the above

5. An ideal PID controller has the transfer function [1 + (1/0.55) + 0.25]. The frequency at which the magnitude ratio of the controller is 1, is________________?

   A. 0.5/0.2
   B. 0.2/0.5
   C. 0.2 × 0.5
   D. 1/√(0.2 × 0.5)

6. The time constant of a unity gain, first order plus time delay process is 5 min. If the phase lag at a frequency of 0.2 rad/min is 60°, then the dead time (in minutes) is________________?

   A. 5π/12
   B. π/6
   C. π/12
   D. π/3

7. Which of following error integral is considered as the best criterion in controller settings ?

   A. ∫0 ∞ |e| dt
   B. ∫0 ∞ |e2| dt
   C. ∫0 ∞ e2 dt
   D. None of these

8. Temperature control of an exothermic chemical reaction taking place in a CSTR is done with the help of cooling water flowing in a jacket around the reactor. The types of valve and controller action to be recommended are________________?

   A. Air to open valve with the controller direct acting
   B. Air to close valve with the controller indirect acting
   C. Air to open valve with the controller indirect acting
   D. Air to close valve with the controller direct acting

9. The transfer function for an ideal proportional plus reset controller (reset time T) is_______________?

   A. Kc[1 + (1/TS)]
   B. Kc(1 + TS)
   C. Kc/(1 + TS)
   D. Kc/[1 + (s/T)]

10. If response of a control system is to be free of offset and oscillation, the most suitable controller is_________________?

    A. Proportional controller
    B. Proportional-derivative (PD) controller
    C. Proportional-integral (PI) controller
    D. Proportional integral-derivative (PID) controller