Search results for "Aerospace"
showing 10 items of 450 documents
An EKF Based Method for Path Following in Turbulent Air
2017
An innovative use of the Extended Kalman Filter (EKF) is proposed to perform both accurate path following and adequate disturbance rejection in turbulent air. The tuned up procedure employs simultaneously two different EKF: the first one estimates gust disturbances, the second one estimates modified aircraft parameters. The first filter, by using measurements gathered in turbulent air, estimates both aircraft states and wind components. The second one, by using the estimated disturbances, obtains command laws that are able to reject disturbances. The predictor of the second EKF uses the estimated wind components to solve motion equations in turbulent air. Besides a set of unknown stability …
Automatic EKF tuning for UAS path following in turbulent air
2018
By using two simultaneously working Extended Kalman Filters, a procedure is implemented in order to perform in a fully autonomous way the path following in turbulent air. To guarantee the robustness of the proposed algorithm, an automatic tuning procedure is proposed to determine optimal values of Process and Measurement Noise statistics. Such a procedure is based on both the characteristics of the disturbances and the desired flight path; in particular, a specific performance index is applied to tune filters. In this way control laws are adapted to the flight condition and these lead to an optimal path-following. This research represents an upload of previous papers. It allows eliminating …
Refitting of an eco-friendly sailing yacht: numerical prediction and experimental validation
2016
A 4.60 m sailing yacht, made with a flax fiber composite and wood, has been refitted with the aim of hull weight reduction and performance improvement during regattas. The first objective was obtained with a lightening of internal hull reinforcements while the second one with a reduction of the maximum beam, in order to minimize the longitudinal moment of inertia. The refitting was first simulated via CAD-FEM interaction to establish the feasibility of the procedure and to verify the structural integrity. The resulting hull was then instrumented with strain gauges and tested under typical rigging and sailing conditions. Results obtained by the numerical modeling and measured from experiment…
Nonlinear model based particle swarm optimization of PID shimmy damping control
2016
The present study aims to investigate the shimmy stability behavior of a single wheeled nose landing gear system. The system is supposed to be equipped with an electromechanical actuator capable to control the shimmy vibrations. A Proportional-Integrative-Derivative (PID) controller, tuned by using the Particle Swarm Optimization (PSO) procedure, is here proposed to actively damp the shimmy vibration. Time-history results for some test cases are reported and commented. Stochastic analysis is last presented to assess the robustness of the control system.
Rewetting of a hot vertical surface by liquid sprays
2005
Hot surfaces rewetting interests several technological fields. A very important application is in nuclear reactors technology, where it governs the cooling of overheated fuel elements during hypothesized loss of coolant accidents (LOCAs). This phenomenon is also important in many normal processes and accidental situations taking place in conventional processes. For example when the integrity of metallic containers, filled by toxic or dangerous substances, is endangered by a hypothetical fire. The rewetting consists in the re-establishment of coolant in contact with metallic surfaces become dried due to high temperature. To this end cold liquid is injected on these surfaces via sprays or other …
Time-resolved velocity measurements in a magnetic micromixer
2015
Abstract Mixing efficiency is lower in passive micromixers due to viscous forces and substantial research effort is focused on designing high performance micromixers. Active micromixers make use of external forces to enhance mixing efficiency. Among these, magnetic forces are popular because they are non-contact and therefore the micromixer design can be kept simple. Laser-based diagnostic tools have great potential in providing multi-parameter information in microfluidics research on mixing. MicroPIV experiments are performed to investigate the transient flow field in a magnetic micromixer undergoing labyrinthine instability. Velocity and interface front information is extracted from a seq…
Enhancement of heat exchanger thermal hydraulic performance using aluminum foam
2018
Abstract This paper deals with an experimental study of a turbulent forced convection in a rectangular channel partly fitted with aluminum metallic foam blocks. Experiments were carried out on samples having a constant porosity of 93.8%, different grades of 5, 20 and 40 PPI, and three different height ratios of 0.6, 0.8 and 1. The blocks were arranged in a baffle like configuration. A constant heat flux of 2 W/cm2 was applied on the bottom wall of the test section, while air velocity was varied from 1 to 5 m·s−1. Temperatures of the wall along the flow direction as well as those of the inlet and outlet sections have been measured. Additionally, pressure drop measurements across the aluminum…
Assessment of a mattress with phase change materials using a thermal and perception test
2017
Abstract Mattresses composed by phase change materials (PCMs) may improve the thermoregulation of the human body. The aim of the study was to analyse the thermoregulatory efficiency of a PCMs and a conventional mattresses via the evaluation of the skin temperature, thermal comfort and thermal perception. Twenty participants lay on a PCMs and a conventional mattress for 20 min in each mattress on the same day. Skin temperature of the back of the participants and temperature of the sheet of the mattresses were measured before and immediately after lying on each mattress. Thermal comfort and thermal perception were also reported during the last minute of the lying test. The PCMs mattress resul…
Multiplicative cases from additive cases: Extension of Kolmogorov–Feller equation to parametric Poisson white noise processes
2007
Abstract In this paper the response of nonlinear systems driven by parametric Poissonian white noise is examined. As is well known, the response sample function or the response statistics of a system driven by external white noise processes is completely defined. Starting from the system driven by external white noise processes, when an invertible nonlinear transformation is applied, the transformed system in the new state variable is driven by a parametric type excitation. So this latter artificial system may be used as a tool to find out the proper solution to solve systems driven by parametric white noises. In fact, solving this new system, being the nonlinear transformation invertible, …
Factors affecting flavor perception in space: Does the spacecraft environment influence food intake by astronauts?
2020
International audience; The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to …