What is the role of integral action in a controller?

Integral action accumulates past errors and adjusts control output until error becomes zero, eliminating steady-state error. As long as any error exists, the integral term keeps changing, driving the system toward zero error. However, integral action adds phase lag, potentially causing instability if gain is too high. It can also cause integral windup when actuators saturate. Anti-windup schemes limit integral accumulation during saturation. Integral action is essential for accurate setpoint tracking.