Optimal Behavior Planning for Autonomous Driving: A Generic Mixed-Integer Formulation

Mixed-Integer Quadratic Programming (MIQP) has been identified as a suitable approach for finding an optimal solution to the behavior planning problem with low runtimes. Logical constraints and continuous equations are optimized alongside. However, it has only been formulated for a straight road, omitting common situations such as taking turns at intersections. This has prevented the model from being used in reality so far. Based on a triple integrator model formulation, we compute the orientation of the vehicle and model it in a disjunctive manner. That allows us to formulate linear constraints to account for the non-holonomy and collision avoidance. These constraints are approximations, for which we introduce the theory. We show the applicability in two benchmark scenarios and prove the feasibility by solving the same models using nonlinear optimization. This new model will allow researchers to leverage the benefits of MIQP, such as logical constraints, or global optimality.Comment: Published at IEEE Intelligent Vehicles Symposium (IV), 202

Modelling the Development of a Regional Charging Infrastructure for Electric Vehicles in Time and Space

This article presents a dynamic spatial model of the development of a charging infrastructure for electric vehicles in the German metropolitan region of Stuttgart. The model consists of several sub-models whose functioning and interactions are explained in detail. The first sub-model simulates the time-spatial development of electric vehicle ownership. The output of this module is used by the second component that determines the resulting demand for charging stations. To quantify this demand, the necessary utilisation of charging stations to allow for the profitability of the infrastructure is calculated. A final processing step simulates the mobility of EVs throughout the Region Stuttgart, and thus allows allocating the need for charging stations in space. We used our model to generate several scenarios of the development of a charging infrastructure in the Region Stuttgart until 2020. The main finding of this work is that the number of public charging stations needed for the region in the long run is quite low. If too many charging stations are installed the infrastructure will be under-utilized and thus cannot be operated economically. The simulation runs show that the installation of public charging infrastructure should be focused on the few biggest urban centres of the region. The scenarios also show that publicly accessible charging stations form only a minor part of the overall number of charging stations. Additionally, it can be seen that the exponential growth of electric vehicle ownership, with very few vehicles at the beginning, but large gains after a few years, requires high flexibility from stakeholders involved in the implementation of charging infrastructure for electric vehicles

Increased tower eigenfrequencies on floating foundations and their implications for large two- and three-bladed turbines

If the tower of a bottom-fixed turbine is put on a floating foundation, such as a spar, semi-submersible, or barge, its eigenfrequency increases. In the investigated case, the tower eigenfrequency rose to about twice its previous value. For bottom-fixed applications, the comparatively high blade-passing frequency of a three-blade turbine (3P) leaves a great bandwidth to design a light and soft tower with a low-enough eigenfrequency. On one of those floaters, however, the eigenfrequency of the same tower might neither be high nor low enough to avoid eigenfrequency excitation by 3P around rated speed. Due to the lower blade passing frequency of a two-bladed wind turbine (2P), the same tower eigenfrequency is high enough by default, enabling considerable material savings or at least eliminating the severe eigenfrequency excitation issue of its bottom-fixed version. Additionally, cost benefits in the whole life-cycle of two-bladed turbines remain. 20MW two- and three-bladed turbines were analyzed numerically on an upscaled version of the UMaine VolturnUS-S semi-submersible, confirming the reasoning.PeerReviewe

Wärmeversorgung in flexiblen Energieversorgungsystemen mit hohen Anteilen an erneuerbaren Energien

Today the discussion about the transformation of the energy system is mainly focused on the increasing renewable share of energy generation by wind and solar power. To achieve the ambitious overall climate policy objectives, the sectors heat generation and traffic must be addressed as well. In this paper the focus is set on the integration of electric heat systems (PtH - Power-to-Heat). By those technologies the future power demand will increase, but on the other hand flexibility of the power system is increased to integrate the fluctuating feed-in of wind and solar power. To balance these effects, a mix of highly efficient systems as heat pumps and very flexible hybrid systems should be integrated in the sys-tem. Even today PtH-technologies are a valuable flexibility option to provide ancillary services, to improve adaptability of CHP-plants and integrate fluctuating renewable energy feed-in. Although the technologies are already available, the regulatory framework and the unequal cost burden of electricity and fossil fuels impedes unlocking these potentials. The presented results were generated within the ETG Task Force “Strom im Wärmemarkt”. The detailed study will be released in April 2015