Adaptive flow rate control of a hydraulic proportional valve

The use of hydraulic proportional valves in industry is becoming increasingly popular as they have better performance than conventional on-off valves and lower cost than servovalves. However, due to significant time delay in valve dynamics, they are currently used for low-accuracy and low-dynamics applications. In this study, an adaptive self-tuning controller is proposed to enable a hydraulic proportional valve to achieve accurate set-point flow rate control. A moving model which reduces the system order and hence reduces the identification effort was used for the controller design. The controller is based on the pole-placement technique which shifts the dominant pole to the desired location. In addition, a predictor has been proposed to overcome the effect of the time delay. Experimental results have shown that the proposed self-tuning controller is better than the conventional PI controller as both transient oscillation and steady-state error shown in the PI control have been significantly reduced. Also, the performance of the closed-loop system is very robust as the system response remains the same under various operating conditions.