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Improved sizing of hydraulic servo-drives through inverse simulation approach using Modelica and modified OpenHydraulics library

The inverse dynamic simulation allows a designer to test the dynamic performance of a closed loop controlled drive without the need to parametrize a feedback controller. Equation based object oriented modeling languages such as Modelica are suitable to build models that can be simulated both, in a forward or inverse fashion. The same model can be used to simulate either in forward fashion or inversely, depending purely on which boundary conditions are specified. To evaluate the usefulness and limitations of the inverse simulation approach for the sizing of a hydraulic servo drive, an open source Modelica library OpenHydraulics is modified to enable inverse simulation. The library is then used for a case study about the sizing of a valve/cylinder hydraulic servo-drive. The inverse simulation supports an intuitive, iterative design approach towards the sizing problem of closed loop controlled drives, such as hydraulic or electric servo drives. The designer can change the size of system components and at any time assess the drive’s efficiency for a typical loading cycle without the need to implement feedback control. It is shown in a test case of an existing hydraulic servo drive of a tooling machine, how changes in design parameters can be instructed through using the inverse simulation approach. In this case, the energy losses could be decreased by 69 %.