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GATE 2026 BT – Question 15

Fundamentals of Biological Engineering · Process Control: Measurement devices, valves, first and second order systems, feedback and feed forward control, P, I and D controllers and tuning · 1 mark · Multiple choice

The transfer function of a Proportional-Integral (PI) controller $G_C(s)$ is given by $G_C(s) = K_C\left(1 + \frac{1}{\tau_Is}\right)$ where $K_C$ is the controller gain, $\tau_I$ is the controller integral time constant and s is the Laplace variable. The role of the integral component of the controller is to ____________.

  1. integrate the difference between the process and manipulated variable
  2. integrate the difference between the set point and disturbance variable
  3. integrate the difference between the set point and the measured variable
  4. integrate the difference between the input and output variable

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Correct answer: (C) integrate the difference between the set point and the measured variable

Explanation

The controller acts on the error $e = $ set point $-$ measured value. The integral term accumulates this error over time, which removes the steady-state offset.