DIGITAL HYDRAULICS CIRCUIT BASED ON PWM FUNCTION FOR CONTROLLING HYDRAULIC ACTUATOR POSITION

Jan Zubair Ahmed; Paweł Śliwiński; Krzysztof Kędzia

DIGITAL HYDRAULICS CIRCUIT BASED ON PWM FUNCTION FOR CONTROLLING HYDRAULIC ACTUATOR POSITION

Abstract

Hydraulic systems are used in many different industries, such as multi-source hydrostatic drive systems. In traditional hydraulic systems, a proportional servo valve is used to control the position of hydraulic actuators. The low energy efficiency and high cost of these control valves are two major problems with these systems. Digital hydraulics is one of the most unique ideas on how to solve these problems. Researchers like digital hydraulics because it is inexpensive, it saves energy, it is not sensitive to contamination, and it has low leakage. In this paper, a digital hydraulic circuit is suggested that uses a fast switching on/off valve instead of servo valves to control the position of a hydraulic actuator. Using a proper PWM duty cycle, the flow that passes through the fast-switching valve is controlled in this way. When the control valve is off, excess pump flow flows straight to the tank instead of going through the relief valve. Therefore, the waste of energy caused by the relief valve is greatly reduced. A robust sliding mode controller (SMC) is used to ensure position tracking even when there are uncertainties.