Which controller action uses the accumulated past errors over time to eliminate steady-state error, but can cause wind-up and slow response?

• A. Proportional Controller
• B. Derivative Controller
• C. Integral Controller
• D. On-Off Controller

Answer: (C)

Integral action sums the error over time by integrating the difference between the setpoint and the process variable. This accumulated past error creates a control signal that grows until the steady-state offset is driven to zero, so it can eliminate steady-state error for constant disturbances or step changes. However, because it relies on the history of error, the response tends to be slower and can overshoot if not tuned carefully, since the integrator adds a memory effect to the loop. If the actuator saturates, the integrator can keep accumulating, causing wind-up, which leads to large corrective efforts once the system comes out of saturation and a sluggish, sometimes oscillatory return. Anti-windup techniques are used to prevent this, but the fundamental behavior described—eliminating steady-state error with potential wind-up and slow response—fits integral action.