Macropore flow at the field scale: predictive performance of empirical models and X-ray CT analyzed macropore characteristics

Predictions of macropore flow is important for maintaining both soil and water quality as it governs key related soil processes e.g. soil erosion and subsurface transport of pollutants. However, macropore flow currently cannot be reliably predicted at the field scale because of inherently large spatial variability. The aim of this study was to perform field scale characterization of macropore flow and investigate the predictive performance of (1) current empirical models for both water and air flow, and (2) X-ray CT derived macropore network characteristics. For this purpose, 65 cylindrical soil columns (6 cm diameter and 3.5 cm height) were extracted from the topsoil (5 to 8.5 cm depth) in a 15 m × 15 m grid from an agricultural loamy field located in Silstrup, Denmark. All soil columns were scanned with an industrial CT scanner (129 μm resolution) and later used for measurements of saturated water permeability, air permeability and gas diffusivity at -30 and -100 cm matric potentials. Distribution maps for both water and air permeabilities and gas diffusivity reflected no spatial correlation irrespective of the soil texture and organic matter maps. Empirical predictive models for both water and air permeabilities showed poor performance as they were not able to realistically capture macropore flow because of poor correlations with soil texture and bulk density. The tested empirical model predicted well gas diffusivity at -100 cm matric potential, but relatively failed at -30 cm matric potential particularly for samples with biopore flow. Image segmentation output of the four employed methods was nearly the same, and matched well with measured air-filled porosity at -30 cm matric potential. Many of the CT derived macropore network characteristics were strongly interrelated. Most of the macropore network characteristics were also strongly correlated with saturated water permeability, air permeability, and gas diffusivity. The correlations between macropore network characteristics and macropore flow parameters were further improved on dividing soil samples into samples with biopore and matrix flow. Observed strong correlations between macropore network characteristics and macropore flow highlighted the need of further research on numerical simulations of macropore flow based on X-ray CT images. This could pave the way for the digital soil physics laboratory in the future

An optimal control approach to real-time vehicle guidance

A newly developed two-level driver model is presented. On the anticipation level, optimal control problems for a reduced vehicle dynamics model are solved repeatedly on a moving prediction horizon to yield near optimal setpoint trajectories for the full model. On the stabilization level, a nonlinear position controller is developed to accurately track the setpoint trajectories with a full motor vehicle dynamics model in real-time. The formulation of the optimal control problems on the anticipation level is based on a nonlinear single track model which is extended by a complex tire model and further nonlinear model details such as to match the main properties of the full vehicle dynamics model. The optimal control problems are solved efficiently by a recently developed sparse direct collocation method. Numerical results for various vehicle maneuvers are presented, including a time-optimal double lane change at high speed

Mensch-Technik-Kooperation und Fahrzeuginnenraum

Kraftfahrzeuge ermöglichen unserer Gesellschaft Mobilität. Mit ihrer Hilfe können Menschen und Güter von einem Ursprungs- zu einem Zielort bewegt und menschliche Bedürfnisse z. B. nach Nahrung, Anerkennung und Selbstverwirklichung gestillt werden. Erreicht werden kann dieses Stillen von Bedürfnissen aber nur durch eine enge Kooperation zwischen Menschen (innerhalb und außerhalb der Fahrzeuge) sowie dem technischen System. So wirken zum Beispiel Fahrende mit Hilfe von Bedienhandlungen zur Längs- und Quersteuerung (d. h. Beschleunigen/Bremsen, Richtungswechsel) auf das Kraftfahrzeug ein