Analysis of Valve Requirements for High-Efficiency Digital Displacement Fluid Power Motors

Digital displacement fluid power motors have been shown to enable high-efficiency operation in a wide operation range, including the part load range where conventional fluid power motors suffers from poor efficiencies. The use of these digital displacement motors set new requirements for the valve technology, as very fast switching and low pressure loss is needed to obtain high-efficient motor operation.
Two central parameters describing the valve operation are the valve switching time and the flow-pressure coefficient. These requirements are important inputs for the mechatronic valve design process, where both the electro-magnetic actuation, the valve moving mass and the material strength is pushed to the limits.
In this present paper a system model describing the digital motor efficiency as a function of valve performance is developed, including a valve opening/closing control method. The valve transition time and flow-pressure coefficient are normalized, leading to a presentation of the general efficiency map of the digital displacement motor. Finally the performance of existing commercial valves with respect to digital motors is commented.