Which technique is specifically used to limit the speed of actuator output changes to prevent instability during saturation?

• A. Anti-windup
• B. Sensor filtering
• C. Rate limiting
• D. Feedforward

Answer: (C)

Limiting how fast the actuator output can change is the technique that directly keeps the system stable when the actuator is near or at its limits. When saturation occurs, the controller can command rapid, large changes that the actuator cannot follow, which can excite the plant’s high-frequency dynamics and lead to instability or oscillations. By enforcing a maximum rate of change, you smooth the commanded signal into a gradual ramp, preventing abrupt moves that push the system into unstable behavior and helping the loop stay within safe operating bounds.

Anti-windup, while important, focuses on preventing integrator buildup during saturation rather than controlling how quickly the actuator can move. Sensor filtering helps reduce noise influence but doesn’t specifically limit the speed of actuator changes. Feedforward improves tracking but doesn’t address rate of change during saturation.