In this paper, we present a novel concept for robustly controlling the attitude of tiltwing aircraft. Our main contribution is the introduction of a wing-fixed coordinate system for angular acceleration control, which forms the basis of a simple and robust attitude controller. Using the wing-fixed coordinate system allows us to describe the actuator effectivity using simple approximations based on the current operating conditions of the aircraft. Coupled with a robust angular rate control concept, which does not rely on an accurate aerodynamic model, we present a controller stabilizing the entire flight envelope of a tiltwing aircraft. The underlying angular acceleration controller uses the concept of Incremental Nonlinear Dynamic Inversion (INDI) to achieve robustness against aerodynamic uncertainties. The resulting controller is evaluated in both simulation studies and flight tests.

Taking complexity of process technology, economical and environmental reasons as well as time impact into account, removal of lead based on intermetallics formation and subsequent separation proves to be the most balanced approach. The hitherto used aggregation agent sodium fluoride does serve as a suitable additive in European countries. Therefore, fluorine-free compound separation is evaluated. Thermochemical modelling of Cu–Zn–Pb–Ca–O system identifies ideal process conditions, namely, charging calcium with an amount of 1.5 wt-% at 930°C. Experiments carried out at stated parameters reveal comprehensive formation of Pb–Ca compounds, chemically similar to the stoichiometric intermetallic phase Ca5Pb3. Thus, the results prove the technological feasibility of lead removal from molten brass scrap using fluorine-free compound separation

Bottom-up process design is performed for a new antimony white fuming approach from antimony-rich lead refining residues. Thermochemical modelling is used to evaluate process boundaries regarding temperature and slag composition allowing the fuming of qualified antimony white from mentioned residues. Two methods are evaluated in laboratory scale to test possibilities of preconditioning for the fuming process. The first one is based on a more selective oxidation during lead softening; the second one on carbothermic reduction of the slag. Antimony enrichment is successfully proven under laboratory scale conditions.

Recently, the concept of incremental nonlinear dynamic inversion has seen an increasing adoption as an attitude control method for a variety of aircraft configurations. The reasons for this are good stability and robustness properties, moderate computation requirements and low requirements on modelling fidelity. While previous work investigated the robust stability properties of incremental nonlinear dynamic inversion, the actual closed-loop performance may degrade severely in the face of model uncertainty. We address this issue by first analysing the effects of modelling errors on the closed-loop performance by observing the movement of the system poles. Based on this, we analyse the neccessary modelling fidelity and propose simple modelling methods for the usual actuators found on small-scale electric aircraft. Finally, we analyse the actuator models using (flight) test data where possible.

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