Groundwater flow and nutrient transport were studied in a riparian meadow during a three-year period. The meadow is situated along a first order stream in the River Gjern catchment area, Jutland, Denmark. Field data included measurements of hydraulic head, hydraulic conductivity and soil characteristics. Groundwater sampled from piezometers was analysed for nitrate, ammonium and phosphate. Nitr...

In general, the position control of electro-hydraulic actuator (EHA) systems is difficult because of system uncertainties such as Coulomb friction, viscous friction, and pump leakage coefficient. Even if the exact values of the friction and pump leakage coefficient may be obtained through experiment, the identification procedure is very complicated and requires much effort. In addition, the ide...

This paper presents the design and experimental evaluation of an explicit force controller for a hydraulic actuator in the presence of signi"cant system uncertainties and nonlinearities. The nonlinear version of quantitative feedback theory (QFT) is employed to design a robust time-invariant controller. Two approaches are developed to identify linear time-invariant equivalent model that can pre...

A range of continental-scale soil datasets exists in Europe with different spatial representation and based on different principles. We developed comprehensive pedotransfer functions (PTFs) for applications principally on spatial datasets with continental coverage. The PTF development included the prediction of soil water retention at various matric potentials and prediction of parameters to ch...

For understanding water and solute transport processes, knowledge about the respective hydraulic properties is necessary. Commonly, hydraulic parameters are estimated via pedo-transfer functions using soil texture data to avoid cost-intensive measurements of hydraulic parameters in the laboratory. Therefore, current soil texture information is only available at a coarse spatial resolution of 25...

− Since November 2008, PTB's force scale has been complemented in the range from 2 to 5 MN by a further force standard machine. This automatically working 5 MN Force Standard Machine (FSM) utilizes the hydraulic amplification of a 50 kN mass stack and enables low uncertainties of smaller than 0.01% by using innovative methods for the control principle and the link-up of the force standard. In t...

A robust teleoperation controller design method for an underwater manipulator is proposed considering the master and the underwater slave separately. To achieve transparency and stability for a teleoperation of an underwater manipulator in unknown environments with time-varying uncertainties such as added mass, buoyancy, hydraulic drag and friction effect, an adaptive sliding mode control schem...

If all parameters influencing sewer performance were known (or deterministic) then the decision making process associated to the planning of sewer replacement should be relatively straightforward. However, when trying to forecast service life, uncertainties arise considering the deterioration process, the variability of sewer pipe properties, environmental conditions or the used information res...

In this paper a robust design process is introduced for a scalar model reference adaptive control (MRAC) algorithm. Three different types of MRAC control rules are reviewed and analysed in the frequency domain. A design process for MRAC is given within the range of plant settling times 0.01-100 seconds which is relevant for a wide range of mechanical systems. By using this design method the MRA...