INVESTIGATION OF A DIGITAL VALVE SYSTEM EFFICIENCY FOR METERING-IN SPEED CONTROL USING MATLAB/SIMULINK.

For a long time, servo and proportional valves have ruled in the flow control field. Since the nearly past decade a new method titled "Digital Valve System" has strived in this area, and has proven some advantages over the elderly valves. The importance of this technique rises because of the inability of analog valves to fulfill fault tolerance, energy efficiency, and manufacture standardization. Also, Digital hydraulics concept has the possibility to be extended to replace traditional pumps, accumulators, transformers, motors and many various valves. Moreover, it manages to raid not only the hydraulic field but also water and pneumatic power systems with acceptable results, when compared to the analog valves. The digital valve system utilizes a pack of simple 2/2 on/off valves to compete versus the analog valves. The Digital Valve Unit (DVU) is composed of parallel connected on/off valves with a common input and common output ports; and the output flow has discrete values. To determine the flow rate of each valve in the Digital Valve Unit (DVU), a Pulse Code Modulation (PCM) scheme was chosen, in which the valves flow rates have discrete values and can be presented as a geometric sequence with common ratio two. This paper studies the Feasibility of metering-in speed control using digital valve system. Through the paper, four cases modeled to describe and evaluate DVS: an ideal case with four and five valves, a near real case with four valves and a particular comparative case of an analog valve. A simple open-loop controller is used for the speed control in case of DVU using Simulink and Stateflow, while with the proportional valve a closed-loop controller is used. The results indicated the possibility to regulate the flow rate in the hydraulic circuit using Digital Unit instead of an analog proportional valve, with a dropping of 93% in energy consumption when compared against a two-way proportional valve. The high efficiency is owing to the lower differential pressure in DVU than with the two-way proportional valve. On the other side, the results show high-pressure peaks with DVU which needs further study. The theory has advantages of high linearity, low hysteresis, less pressure drop at small flow rates, and fault tolerance. The biggest challenges related to DVU can be summarized to a great package size and valve states uncertainty. [ABSTRACT FROM AUTHOR]