Mathematical Model of Unmanned Aircraft In Ground Effect for Optimal Collision Avoidance

The fundamental aim of the present paper is to model the aerodynamic characteristics of an Unmanned Aerial Vehicle(UAV) flying in ground effect. The second aim is to determine the relationship between the optimal avoidance maneuver and the control to execute it. In fact, this relationship is basilar to the development of a guidance scheme capable of approximating the optimal trajectory in real time. In the first part of this work ,a non-linear model is built in order to model the aerodynamic characteristics of an UAV flying In Ground Effect. To use a single model in the whole range of flying altitude, aerodynamic coefficients are modeled by means of hyperbolic equations. In particular, these ones depend on the ground distance. Such a model is employed to describe aerodynamic forces and moments in the equations of motion which are used in order to obtain optimal trajectories for solving the collision avoidance problem

Gain scheduling automatic landing system by modeling Ground Effect

Taking ground effect into account a longitudinal automatic landing system is designed. Such a system will be tested and implemented on board by using the Preceptor N3 Ultrapup aircraft which is used as technological demonstrator of new control navigation and guidance algorithms in the context of the “Research Project of National Interest” (PRIN 2008) by the Universities of Bologna, Palermo, Ferrara and the Second University of Naples. A general mathematical model of the studied aircraft has been built to obtain non–linear analytical equations for aerodynamic coefficients both Out of Ground Effect and In Ground Effect. To cope with the strong variations of aerodynamic coefficients In Ground Effect a modified gain scheduling approach has been employed for the synthesis of the controller by using six State Space Models. Stability and control matrices have been evaluated by linearization of the obtained aerodynamic coefficients. To achieve a simple structure of the control system, an original landing geometry has been chosen, therefore it has been imposed to control the same state variables during both the glide path and the flare

An Algorithm for Parameter Identification of UAS from Flight Data

The aim of the present work is to realize an identification algorithm especially devoted to UAS (unmanned aerial systems). Because UAS employ low cost sensor, very high measurement noise has to be taken into account. Therefore, due to both modelling errors and atmospheric turbulence, noticeable system noise has also to be considered. To cope with both the measurement and system noise, the identification problem addressed in this work is solved by using the FEM (filter error method) approach. A nonlinear mathematical model of the subject aircraft longitudinal dynamics has been tuned up through semi-empirical methods, numerical simulations and ground tests. To take into account model nonlinearities, an EKF (extended Kalman filter) has been implemented to propagate the state. A procedure has been tuned up to determine either aircraft parameters or the process noise. It is noticeable that, because the system noise is treated as unknown parameter, it is possible to identify system affected by noticeable modelling errors. Therefore, the obtained values of process noise covariance matrix can be used to highlight system failure. The obtained results show that the algorithm requires a short computation time to determine aircraft parameter with noticeable precision by using low computation power. The present procedure could be employed to determine the system noise for various mechanical systems, since it is particularly devoted to systems which present dynamics that are difficult to model. Finally, the tuned up off-line EKF should be employed to on-line estimation of either state or unmeasurable inputs like atmospheric turbulence

AUTOMATIC TAKE-OFF OR LANDING PATH FOLLOWING IN TURBULENT AIR FOR UAS - AN EKF BASED PROCEDURE

By using the Extended Kalman Filter (EKF) an accurate take-off or landing flight path following in turbulent air is performed. The tuned up procedure employs simultaneously two different EKF: the first one estimates gust disturbances, the second one affords to determine the necessary controls displacements for rejecting those ones. In particular, the first filter, by using instrumental measurements gathered in turbulent air, estimates wind components. The second one obtains command laws able to follow the desired flight path. To perform this task aerodynamic coefficients have been modified by adding entirely new derivatives or synthetic increments to basic ones whose might the kind of change required to reject disturbances. Such a procedure leads to a set of unknown stability and control parameters containing the required displacements of the controls. The modified aircraft parameters are determined by augmenting the aircraft’s state. The filter estimates the new set of aircraft stability derivatives by using measurements made by the desired take-off or landing flight path parameters. Once the unknown stability and control derivatives have been determined, the obtained control displacements are used to perform an accurate path following in turbulent air. Obviously, the obtained control laws are adaptive since they depend by either the characteristics of the disturbance or the desired flight path. The proposed procedure requires low computational power, therefore it is particularly suited for UAS, besides being simple to implement on board it may be successfully employed on low cost platforms

FLIGHT CONTROL RESEARCH LABORATORY UNMANNED AERIAL SYSTEM WIND SHEAR ON-LINE IDENTIFICATION

An algorithm to perform the on line identification of the wind shear components suitable for the UAS characteristics has been implemented. The mathematical model of aircraft and wind shear in the augmented state space has been built without any restrictive assumption on the dynamic of wind shear. Because of the strong velocity variations typical of wind shear induce severe accelerations on the aircraft the wind shear effects have been modeled as external forces and moments applied on the aircraft. The identification problem addressed in this work has been solved by using the Filter error method approach. An Extended Kalman Filter has been developed to propagate state. It has been tuned by using a database of measurements through off-line identification of the process noise covariance matrix. Afterwards the implemented EKF has been employed to estimate onboard either aircraft state or turbulence, with significant savings in terms of time and computing resources. Robustness of implemented algorithm has been verified by means of several tests. The obtained results show the feasibility of the tuned up algorithm. In fact it is possible, by using a few numbers of low cost sensors, to estimate with a noticeable accuracy the augmented state vector. Besides a very short computation time is required to performthe augmented state estimation even by using low computation power

Time and material. Interdisciplinary study for dating St. Francesco convent in Cagliari (XIII-XXI century)

This study concerns the Franciscan monastery, situated in the historic centre of Cagliari (Sardinia, Italy). It was founded in the 13th century, and transformed up to the present day. Its historical-stratigraphical complexity and the lack of data about its evolution led us to carry out an interdisciplinary inquiry. The investigation began with the use of a laser scanner survey aimed at defining a chronological hypothesis applied to the building which was based on reconstruction of historical maps, examination of masonry techniques and stratigraphic analyses. The dating obtained led to the choice of masonry samples to compare with other local and contemporary buildings where the chronology is well-known with the aim of confirming previous hypothesis. Analysis of the masonry samples allowed an understanding of their actual structure and composition, with reference to specific historical events. The mineralogical-petrographic characterization of building materials was essential. Plaster and mortar have been studied with instrumental techniques (OM, X-Ray diffraction) to analyze their components. The data obtained lead to a better knowledge of the Franciscan complex and this is essential for a restoration project respecting all its historical signs. The data is also very useful for dating other local buildings characterized by the same masonry techniques

An experimental investigation on air quality inside WindJet aircraft

ABSTRACT In order to improve the passengers and crew comfort during the flight, the aim of the present paper is a study of the cabin air quality through experimental measures on randomly selected flight segments of an Italian airline company, WindJet. Carbon dioxide, ultrafine particles, temperature and relative humidity have been measured by using low cost high efficiency instrumental equipments. Exploring ways to improve aircraft cabin air quality, WindJet and University of Palermo are investigating equipment, filters and components of the ventilation system. In this paper, after description of both ventilation systems for aircrafts of WindJet and the instrumental equipments used to measure environmental characteristics on board, obtained results are shown

Analysis of the interaction of calcitriol with the disulfide isomerase ERp57

Calcitriol, the active form of vitamin D3, can regulate the gene expression through the binding to the nuclear receptor VDR, but it can also display nongenomic actions, acting through a membrane- associated receptor, which has been discovered as the disul de isomerase ERp57. The aim of our research is to identify the binding sites for calcitriol in ERp57 and to analyze their interaction. We rst studied the interaction through bioinformatics and uorimetric analyses. Subsequently, we focused on two protein mutants containing the predicted interaction domains with calcitriol: abb’- ERp57, containing the rst three domains, and a’-ERp57, the fourth domain only. To consolidate the achievements we used the calorimetric approach to the whole protein and its mutants. Our results allow us to hypothesize that the interaction with the a’ domain contributes to a greater extent than the other potential binding sites to the dissociation constant, calculated as a Kd of about 10−9 M

Passives are not hard to interpret but hard to remember : evidence from online and offline studies

Passive sentences are considered more difficult to comprehend than active ones. Previous online-only studies cast doubt on this generalization. The current paper directly compares online and offline processing of passivization and manipulates verb type: state vs event. Stative passives are temporarily ambiguous (adjectival vs verbal), eventive passives are not (always verbal). Across 4 experiments (self-paced reading with comprehension questions), passives were consistently read faster than actives. This contradicts the claim that passives are difficult to parse and/or interpret, as argued by main perspectives of passive processing (heuristic or syntactic). The reading time facilitation is compatible with broader expectation/surprisal theories. When comprehension targeted theta-roles assignment, passives were more errorful, regardless of verb type. Verbal WM measures did not correlate with the difference in accuracy, excluding it as an explanation. The accuracy effect is argued to reflect a post-interpretive difficulty associated with generating/maintaining a propositional representation of passives required by specific tasks