What is the purpose of anti-windup in control systems?

• A. To prevent sensor drift
• B. To prevent integrator windup when the actuator saturates
• C. To reduce output latency
• D. To improve measurement accuracy

Answer: (B)

The idea is to stop the integrator from accumulating when the actuator cannot respond due to limits. In many controllers, the integral term keeps adding error over time. If the actuator hits its maximum or minimum and can’t follow the controller’s demand, the integrator keeps growing, building up a large stored output. When the system later comes back within its reachable range, that accumulated value can cause a big, delayed surge—overshoot, oscillations, and slow recovery.

Anti-windup schemes address this by tying the integrator to the actual actuator behavior. When saturation is detected, the integrator is reduced, clamped, or adjusted (for example, via back-calculation or conditional integration) so it stops winding up in the saturated region. This keeps the controller’s internal state in sync with what the actuator can actually achieve, leading to less overshoot and quicker, more stable responses once the system leaves saturation.

So, the purpose is to prevent integrator windup that occurs during actuator saturation, not to fix sensor drift, latency, or measurement accuracy.