QUESTION 1
For the closed-loop control system shown above the gain, K, is changed from 1 to 10. The effect on the closed-loop system time constant will be to:
(1) leave it unchanged
(2) increase it by a factor of 10
(3) decrease it by a factor of 10
(4) decrease it by a factor of 5.5
(5) increase it by a factor of 5.5
QUESTION 2
The diagrams above show four Bode plots of uncompensated and compensated performance for a particular control system. Which diagram shows the effects of adding phase-lag compensation?
(1) the diagram labelled 1
(2) the diagram labelled 2
(3) the diagram labelled 3
(4) the diagram labelled 4
QUESTION 3
A phase-lead compensator could be added to a control system when it is desirable to:
(1) improve the steady-state accuracy
(2) speed up the system response
(3) improve the system stability margin(s)
(4) both (1) and (3) above
(5) both (2) and (3) above
QUESTION 4
Part(s) of the characteristics of an 'ideal' controller can best be described as:
(1) high gain at low frequencies to reduce steady-state errors
(2) high gain at mid frequencies for rapid response to transient changes
(3) low gain at high frequencies so that oscillations (overshoots) die out rapidly
(4) all of the above
(5) none of the above
QUESTION 5
The diagram above shows a block diagram of a three-term controller. Which one of the blocks corresponds to the derivative action term?
(1) the block labelled 1
(2) the block labelled 2
(3) the block labelled 3
(4) the block labelled 4
(5) none of the above
QUESTION 6
The major advantage(s) of pneumatic control systems over hydraulic control systems is/are:
(1) air is not flammable
(2) air, being compressible, is easier to control
(3) air can be recycled more easily
(4) all of the above
QUESTION 7
A pneumatic P-D controller is shown in the diagram above. This controller is being used to control an output that shows excessive overshoot. To decrease this overshoot it would be best to:
(1) reduce the opening through the derivative restriction
(2) increase the opening through the derivative restriction
(3) reduce the 'stiffness' of the bellows
(4) increase the overall supply pressure
QUESTION 8
The same pneumatic P-D controller as in question 7, is in use. To reduce the controller output pressure it would be best to:
(1) reduce the opening through the derivative restriction
(2) increase the opening through the derivative restriction
(3) reduce the 'stiffness' of the bellows
(4) increase the overall supply pressure
QUESTION 9
The time delay between material being fed onto the conveyor belt and arriving at the weighing
station is:
(1) there is no delay
(2) 0.67 s
(3) 0.80 s
(4) 0.96 s
(5) 1.20 s
QUESTION 10
The direct transmission gain of the system is:
QUESTION 11
The loop gain of the system (expressing any time delay as ? seconds) is:
QUESTION 12
The gain cross-over frequency for this system is best estimated as:
(1) not speci?ed: the gain is always less than 0 dB
(2) 0.75 rad/s
(3) 0.9 rad/s
(4) 1 rad/s
(5) 1.2 rad/s
QUESTION 13
The open-loop system phase margin is best estimated as:
(1) 17°
(2) 21°
(3) 50°
(4) 90°
(5) 120°
QUESTION 14
The gain margin of the system is best estimated as:
(1) 4 dB
(2) 17 dB
(3) 20 dB
(4) 23 dB
(5) 40 dB
Data for questions 15-17
The system is assumed to be running as a closed-loop system.
A step change of size 5 units (volts) is made in the required amount of material/unit-length setting.
The following questions 15 - 17 refer to the effects of this change.
QUESTION 15
The system response would be best described as:
(1) sluggish
(2) almost critically damped
(3) slightly underdamped
(4) lightly damped
(5) unstable
QUESTION 16
The amount of peak-percentage overshoot exhibited by the system would best be estimated as:
(1) none
(2) 20%
(3) 40%
(4) 60%
(5) 100%
QUESTION 17
The change in the actual amount of material per unit length will be:
(1) 0
(2) 1.25 kg/m
(3) 1.67 kg/m
(4) 3.0 kg/m
(5) 5.0 kg/m
Data for questions 18-20
A change in the plant layout means the weighing station has to be shifted 0.3 m further away from the hopper.
QUESTION 18
Which one of the following statements best expresses the effect of this change on the control system performance?
(1) There will be no change in system performance.
(2) The overall system performance will be improved.
(3) The overall system performance will be made worse.
QUESTION 19
The change in plant layout mentioned in question 18 has been made. The system is required to respond to changes with less overshoot.
Which one of the following options would be the best to choose?
(1) P-I control
(2) P-I-D control
(3) proportional control
(4) phase-lead compensation
(5) phase-lag compensation
QUESTION 20
A fault causes the conveyor belt to suddenly run at a lower speed.
Which one of the following statements best describes the response of the system to this fault?
(1) Less material/unit length is delivered.
(2) More material/unit length is delivered.
(3) There should be no long-term change in the rate of material delivery.
Attachment:- questions.pdf