Intelligent Digital Controller Design and Experimental Implementation for a Digital Hydraulic Lifting System

This paper examines the enhancement of hydraulic performance through the replacement of a proportional valve with a Digital Valve Unit (DVU) for flow control purposes. The study underscores the significance of proportional hydraulic valves in precise flow regulation, while concurrently acknowledging that efficiencies in flow control may adversely affect the operational efficacy of actuators, particularly in hydraulic lifting systems. The digital valve system uses simple on/off solenoid valves arranged in parallel and integrated with an intelligent controller, designed utilizing a Programmable Logic Controller (PLC) to compete with conventional valves. To this end, both theoretical and experimental evaluations were conducted to compare the performance of the digital and proportional valve systems. The intelligent digital controller operates with discrete flow rates based on geometric sequence, ensuring precise modulation, while the proportional valve uses continuous flow regulation in a closed-loop system. The results revealed that the digital valve system had a 97.8% improvement in energy efficiency, referring to its lower differential pressure. The digital system also exhibited superior linearity and reduced pressure drop at low flow rates; however, its large package size posed a challenge. The proposed configuration was tested through simulations and practical implementation with the PLC, demonstrating its flexibility in adapting to various flow control needs in hydraulic lifting systems. In conclusion, the Digital Hydraulic System (DHS) offers a promising solution for meter-in flow control, providing enhanced performance in hydraulic applications.