Project ForgeInstrumentation & Process Control
Controller Modes
GATE 2015
Hard
Gd^open(s) is the open-loop disturbance transfer function; Gd^closed(s) is the corresponding closed-loop (proportional-control feedback) disturbance transfer function. Which is ALWAYS correct?
- AO[Gd^open(s)]=O[Gd^closed(s)]
- BO[Gd^open(s)]≠O[Gd^closed(s)]
- CO[Gd^open(s)]≥O[Gd^closed(s)]
- O[Gd^open(s)]≤O[Gd^closed(s)]
Explanation
Closing the loop adds the characteristic-equation denominator (1+GcGpGm), which generally introduces additional poles, so the closed-loop order is always ≥ the open-loop order.
Source: GATE CH 2015 (2015)
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