Energy-Efficient Position Tracking For Digital Hydraulic Systems Using Fast-Switching Valve

Hydraulic actuators are widely used where high-magnitude forces are exerted; however, they suffer from low energy-efficiency in many cases. To address this issue, there has been a surge in the volume of researches devoted to improving the efficiency of electro-hydraulic servo systems. Digital Hydraulics is the most recent method, proposed by many researchers to improve the efficiency of hydraulic actuators. Low cost and better energy efficiency are two major advantage of these systems that make them popular among researchers. This paper discusses the possibility of using a fast-switching on/off valve in a novel way, instead of servo valves to improve the efficiency of these systems. For this purpose the flow running through the fast-switching valve controlled, employing proper duty cycle. The excess pump flow is discharged to the tank directly instead of going through the relief valve when the valve is off. Thus the wasted energy, caused by the relief valve, is reduced significantly. A nonlinear backstepping controller is designed to control the duty cycle of the PWM signal of the on/off valve. The effectiveness of this method is tested after conducting experiments on a hydraulic test rig and presenting the experimental results.