Design of thrust vectoring attitude control system for lunar lander flying testbed

The proposed work has been developed within the project LEAPFROG (Lunar Entry and Approach Platform For Research On Ground) at the University of Southern California. The project concerns the realization of a lunar lander test bed prototype with the aim of testing GNC algorithms for simulated lunar flight and descent. The main focus is the realization of a newly designed thrust vectoring system (TVC) that exploits the thrust given by a main engine in order to control the attitude of the platform. This new attitude control system is combined with current traditional reaction control system (RCS) based on cold-gas thrusters. After a preliminary hardware design phase, a linear LQR controller, based on a reduced quaternion model, and a non-linear sliding mode controller are designed for the TVC system. Linear Quadratic Regulator offers a simple implementation, an optimal control law. However it can be affected by un-modeled dynamics and the solutions provided are, in general, only locally valid. Sliding mode control (SMC) guarantees robustness against disturbances, unmodeled dynamics and uncertainties about the mass properties of the prototype, offering also a global stability. Cons of this method are the hard implementation and the request of an high-frequency actuation. A MATLAB/Simulink simulation is set up in order to validate and compare the designed controllers and to analyze if the thrust vectoring system leads to the desired results

Every cloud has a silver lining: how abiotic stresses affect gene expression in plant pathogen-interactions.

The current context of environmental and climate changes deeply influences the outcome of plant-pathogen interactions. Indeed, nowadays it is clear that abiotic stresses strongly affect biotic interactions at various levels. For instance, physiological parameters such as plant architecture and tissue organization along with primary and specialized metabolism are affected by environmental constraints, thus making the plant a more or less worthy host for a given pathogen. Moreover, abiotic stresses can affect the timely expression of plant defense and pathogen virulence. Indeed, several studies have shown that variations in temperature, water and mineral nutrient availability impact plant defense gene expression. Virulence gene expression, known to be crucial for disease outbreak, is also affected by environmental conditions, potentially modifying existing pathosystems and paving the way for emerging pathogens. The present review summarizes the current knowledge on the impact of abiotic stress on biotic interactions at the transcriptional level in both the plant and the pathogen side of the interaction. We performed a meta-data analysis of four different combinations of abiotic and biotic stresses. 197 modulated genes were common to all four combinations, with a strong defense-related GO term enrichment. We also describe the multistress-specific responses of selected defense-related genes.info:eu-repo/semantics/publishe