1,720,990 research outputs found
On the Application of a Vortex Lattice Method to Lifting Bodies Close to a Free Surface
No full textThe interaction of the free surface with either lifting and non lifting, submerged, bodies moving beneath it is of primary interest in naval architecture. Indeed, there are many examples of possible applications such as rudders, stabilizer fins, hydrofoils among the others. The hydrodynamic problem of a submerged lifting body moving close to a free surface presents several complexities that need to be properly addressed in order to achieve a reliable solution. The problem is studied in the framework of a potential flow theory and solved by using an ad-hoc developed Vortex Lattice Method (VLM). The developed method is described and validated by comparison against available data on a flat plate. The analysis then focuses on the convergence properties of the method, especially with respect to the panel dimensions used for the free surface discretization, and on a sensitivity with respect to some peculiar operating parameters such as the depth of the body with respect to the free surface and the angle of attack with respect to the incoming flow
Model Predictive Control for the Scheduling of Seedings in an Adaptive Vertical Farm
No full textA model predictive control approach is presented for the scheduling of sowings in an adaptive vertical farm, i.e., an innovative vertical greenhouse in which the spacing between shelves is automatically adapted to crop growth. First, a dynamic model describing the evolution of occupancy and shelf height is developed. The model is affected by disturbances to account for possible deviations of crop growth from the nominal pattern. Then, an optimal control problem over a given timeframe is defined to determine the best time instants to perform seedings in the various shelves with the goal of maximizing production yield. The repeated solution of the optimal control problem over a shorter, moving window over time, according to the receding horizon paradigm, allows to devise robust control strategies with respect to disturbances, even in the absence of predictions about their future realizations. Preliminary simulation results are reported for different control horizons and type of disturbances to showcase the effectiveness of the proposed approach in maximizing production yield while exploiting almost all the available vertical space
Drone swarms in fire suppression activities: A conceptual framework
No full textThe recent huge technological development of unmanned aerial vehicles (UAVs) can provide breakthrough means of fighting wildland fires. We propose an innovative forest firefighting system based on the use of a swarm of hundreds of UAVs able to generate a continuous flow of extinguishing liquid on the fire front, simulating the effect of rain. Automatic battery replacement and extinguishing liquid refill ensure the continuity of the action. We illustrate the validity of the approach in Mediterranean scrub first computing the critical water flow rate according to the main factors involved in the evolution of a fire, then estimating the number of linear meters of active fire front that can be extinguished depending on the number of drones available and the amount of extinguishing fluid carried. A fire propagation cellular automata model is also employed to study the evolution of the fire. Simulation results suggest that the proposed system can provide the flow of water required to fight low-intensity and limited extent fires or to support current forest firefighting techniques
Scheduling Landing and Payload Switch of Unmanned Aerial Vehicles on a Single Automatic Platform
No full textWe focus on the problem of optimally managing a set of unmanned aerial vehicles performing given missions that require to land on an automatic platform, unmount the currently-carried payload, and take off with another payload to complete mission objectives. Such a problem often arises when swarms of drones cooperate to complete monitoring applications or other tasks requiring an efficient schedule of landings and payload switches in a resource-constrained environment. First, the problem is formulated as a mixed-integer linear programming one, which, however, may be complex to be solved for a large number of drones. Thus, we also propose a heuristic algorithm able to find suboptimal solutions with a reduced computational effort. Preliminary simulation results are reported and discussed
Mixed-Integer Linear Programming for the Scheduling of Seedings in an Industrial Adaptive Vertical Farm
No full textWe present a new concept of industrial vertical greenhouse, called adaptive vertical farm, based on the possibility of adapting the distance between the shelves to the growth of the plants cultivated therein. This is possible through a set of sensors able to measure the crop height and a set of actuators to automatically move the shelves. A scheduling approach of seedings is proposed that requires the solution of a mixed-integer linear programming problem to fully utilize all the available vertical space and maximize the production yield. Simulation results obtained when cultivating various types of crops and for different greenhouse configurations in terms of total height and number of shelves are reported. The goal is to evaluate the effectiveness of the proposed scheduling approach and of the adaptive vertical farm concept in general, as compared to a vertical farm with fixed shelves
LMI based H∞ Observer Design for a Quadcopter Model Operating in an Adaptive Vertical Farm
No full textThe adaptive vertical farm is an innovative solution to increase production yield through adaptive management of available volume. The latest technological advances in data processing and actuators have made UAVs useful in precision agriculture because of their ability to monitor small areas. This paper proposes a H∞ observer design via Linear Matrix Inequalities (LMI) aiming to provide accurate state estimation of an indoor quadrotor operating in an adaptive vertical farm. A new less conservative LMI condition is applied to solve the H∞ circle criterion design. A simulation is given to illustrate the validity and effectiveness of the proposed observer
Parameter estimation of fire propagation models using level set methods
No full textThe availability of wildland fire propagation models with parameters estimated in an accurate way starting from measurements of fire fronts is crucial to predict the evolution of fire and allocate resources for firefighting. Thus, we propose an approach to estimate the parameters of a wildland fire propagation model combining an empirical rate of spread and level set methods to describe the evolution of the fire front over time and space. The estimation of parameters affecting the rate of spread is performed by using fire front shapes measured at different time instants as well as wind velocity and direction, landscape elevation, and vegetation distribution. Parameter estimation is done by solving an optimization problem, where the objective function to be minimized is the symmetric difference between predicted and measured fronts at different time instants. Numerical results obtained by the application of the proposed method are reported in two simulated scenarios and in a case study based on data originated by the 2002 Troy fire in Southern California. The obtained results showcase the effectiveness of the proposed approach both from qualitative and quantitative viewpoints
Adaptive Vertical Farm for Fresh Food Production in Orbital Stations and Future Lunar Settlements
No full textWe propose an adaptive vertical farm that can be installed in orbital stations and future lunar settlements to produce fresh food for astronauts. Such an innovative greenhouse is based on the idea of progressively adapting the height of the various shelves to the growth of the plants, instead of fixing the height of the shelves to the maximum growth, as commonly done in the case of vertical farms with fixed shelves. The main advantages are the need of conditioning a reduced space as compared to fixed-shelves installations, thus resulting in a reduced energy consumption per unit of production, and the increase of the overall production owing to the possibility of installing a larger number of shelves in the same vertical space. The full efficiency of the proposed adaptive vertical farm requires an optimal scheduling of sowings, for which a mixedinteger linear programming problem is devised with the aim of maximizing the number of seedings, while fully exploiting the total height of the greenhouse. Numerical results in comparisons with a vertical farm with fixed shelves showcase the effectiveness of the proposed ideas
Moving Horizon Trend Identification Based on Switching Models for Data Driven Decomposition of Fluid Flows
No full textModal decomposition is pretty popular in fluid mechanics, especially for data-driven analysis. Dynamic mode decomposition (DMD) allows to identify the modes that describe complex phenomenona such as those physically modelled by the Navier-Stokes equation. The identified modes are associated with residuals, which can be used to detect a meaningful change of regime, e.g., the formation of a vortex. Toward this end, moving horizon estimation (MHE) is applied to identify the trend of the norm of the residuals that result from the application of DMD for the purpose to automatically classify the time evolution of fluid flows. The trend dynamics is modelled as a switching nonlinear system and hence an MHE problem is solved in such a way to monitor the time behavior of the fluid and quickly identify changes of regime. The stability of the estimation error given by MHE is proved. The combination of DMD and MHE provide successful results as shown by processing experimental datasets of the velocity field of fluid flows obtained by a particle image velocimetry
LMI Feasibility Analysis in Observer Design for Some Families of Nonlinear Systems
No full textThis note deals with observer design for nonlinear systems via Linear Matrix Inequalities (LMIs). The main goal consists of showing that for some families of nonlinear systems, the LMI-based observer design techniques always provide exponential convergent observer. Indeed, until now, this advantageous feature is unique to some types of observers/estimators, such as the high-gain observer, the sliding mode observer, and the moving horizon estimator, under certain conditions of detectability or observability. More specifically, the LMI conditions we propose in this paper always provide solutions to both systems in companion form and feedforward structure. An extension to a general class of nonlinear triangular systems without linear components is provided, which renders the applicability of LMI-based methods possible for a wide class of nonlinear systems without the need for nonlinear diffeomorphism-based transformations
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