In an automatic boiler control system, which integral controller action is used to return to set point after a disturbance?

In an automatic boiler control system, the integral controller action is essential for correcting the steady-state error that may occur after a disturbance. The integral action continuously sums the errors over time, effectively accumulating the past deviations from the set point. When a disturbance affects the system, the controller's integral action will respond to this cumulative error, driving the process variable back to the desired set point.

This characteristic of the integral component is crucial in ensuring that any persistent offset from the target value is mitigated. It accomplishes this by adjusting the controller output until the error is minimized. Through this method, the integral controller ensures that the system not only reacts to the changes induced by disturbances but also gradually eliminates any steady-state error that results from these disturbances.

In contrast, the other controller actions do not primarily focus on correcting sustained discrepancies over time. Proportional control adjusts the output based on the immediate error but does not account for the accumulated past error, which may leave some steady-state error uncorrected. Feedforward control anticipates disturbances and adjusts output proactively but does not correct past errors by itself. Finally, the term "response" is less specific in this context and is not typically used to describe a controller action like integral, proportional, or feedforward control.