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Designing Fast Switching Valves (FSVs) for digital displacement units is a complicated process pushing the technology to the limit. The system dynamics and the interaction of the fluid, mechanical structure, actuator and control hence calls for advanced modelling, including CFD and FEA, to capture, e.g. fluid stiction effects, end-damping and impact contact stresses. Unfortunately, this essentially renders optimization processes infeasible due to the computational burden involved, although this is precisely what is required for this type of complex multi-domain problem. Therefore, the focus of the current article is on how a complex mechatronic design problem, like designing an FSV, may be aided by considering decomposing and simplification through sensitivity analysis and analyzing correlations between the design and output parameters. This is done to significantly reduce the original design problem without compromising the investigated design space. The paper focuses specifically on the results related to an FSV and the flow delivering part of this, showing the influence of the various design parameters. However, the approach and considerations may be generalized to an other areas as well.

This paper presents a conceptual study aiming to improve the compactness of electro-hydraulic compact drives (ECD ). In most current ECD architectures, gas accumulators are used as volume compensators for the flow imbalance emerging whenever asymmetric single rod cylinders are used. To stay within a required reservoir pressure range typically from two to four bar, a large gas volume is required, compromising system compactness. Combining conventional ECD architectures with a bootstrap reservoir offers a greater degree of freedom in system design, which enables downsizing or avoidance of the gas volume. Another potential benefit by including a bootstrap reservoir is the possibility of elevating the backpressure of the ECD thus enhancing drive stiffness, expanding the application range and market acceptance. Based on an open analysis of the solution space occurring when introducing a bootstrap reservoir, three system architectures are selected for a conceptual study. The results show that the downsizing potential is strongly dependent on the maximum friction force and the area ratio of the bootstrap reservoir pistons, while a linear analysis reveals that for some system architectures the bootstrap reservoir may severely influence the system dynamics. Simulation results confirm the functionality of the proposed system architectures, and show that a potential for downsizing/avoiding the gas volume, as well as increasing the ECD stiffness is present.