PLL in cooperated with PI controller for flow control system

Presents a flow control system using the phase-locked loop technique in cooperation with a PI controller. The PI controller is utilized to pull the flow rate of the system into the phase-locked loop locking range and the steady state flow rate is controlled later by the phase-locked loop. An experimental system is implemented to evaluate the performance of the flow control system using the proposed control method. The experimental results in control the system in the laboratory show that the overshoot is approximately 10% for the 50% step input of the maximum flow rate and the steady-state error is smaller than ±2%. The experimental results also indicate that the effect of load disturbance is rapidly rejected