Energy efficiency improvement of water hydraulic fluid switching transmission

This study aims to determine effective methods for improving the energy efficiency of a water hydraulic Fluid Switching Transmission (FST). This paper introduces three methods to reduce energy consumption: lowering the velocity of the electric motor and stopping the motor during the working and deceleration phases, respectively (first method); restricting the working pressure within a certain range by using an unload valve (second method) or using the idling stop method (third method). Next these three methods are analyzed and compared. Experimental results show that by using the proposed methods, the energy and net energy consumption are greatly reduced. The greatest reductions are from 71.5 to 78.3% for energy consumption and from 65.1 to 66.2% for net energy consumption, corresponding to variations in the reference velocity from 600 to 1000 min −¹. Additionally, the steady state errors in the proposed methods are slightly decreased in the working phase while the transient responses are almost the same for all cases.