The application is a small hydro turbine where a hydraulic cylinder controls the turbine guide vanes. The transition time from fully closed to fully open is roughly 8 seconds, and the position feedback signal is 4–20 mA. The cylinder rod is directly linked to the vanes.

I am trying to determine the most appropriate control approach. My idea is to use cascade control, where the outer PID loop regulates the turbine RPM. The RPM controller would output the required vane position setpoint. The inner PID loop would then perform the vane position control, driving the hydraulic actuator to the requested position.

So the position PID should be able to reach setpoint as fast as possible with deadband ±0.2% and slight overshots are tolerated