Parameter Identification as a Tool for Fluid Power System Development

The dynamic behaviour of fluid power systems depends on a large number of parameters such as the mass of a moving part, the chamber volume, spring stiffness, orifice geometry, leakage, and friction. Some of these quantities are exactly known from the system design or can easily be measured in experiments. Other characteristics are difficult to predict. For instance, the relationship between pressure and flow-rate at orifices with complicated geometry or flowinduced forces on moving valve spools cannot be predicted without extensive CFD simulations. During the design of a fluid power component or system, such uncertainties are often bridged with simple models like the well known equation for flow through sharp-edged orifices. However, the discrepancy between such simple models and the real system behaviour may result in prototype malfunction. Parameter identification can be used to find the differences between the desired system dynamics and the prototype behaviour. This paper shows the use of a state-space system identification approach for the measurement of unknown parameters in a switching-type hydraulic drive.