3,153 research outputs found
Modal Coupling in Presence of Dry Friction
No full textIn this paper, we analyze the behavior of a single pad system in the presence of dry friction. The goal is to investigate the path that leads a stable mechanical system to unstable behavior. In doing so, we studied the behavior of a discrete three DOF model, a continuous model and a finite element model of the pad. The numerical results are consistent with the experimental investigation conducted on a brake disk for railway application
Control design for an under-actuated UAV model
No full textUnmanned Aerial Vehicles (UAV), are increasingly being adapted and used in civil contexts, with particular specialization in the monitoring of the territory for environmental purposes, civil protection or possibly control and inspection of inaccessible areas or dangerous sites. This concerns, in particular, the adaptation of mini-UAVs, small devices that, due to their manageability and costs, can be allocated for public services.For this reason, it was decided to develop a multibody model of a quadrotor copter in the presence of wind fields by using SimScape Multibody Environment. The quadrotor is modelled as a non-linear underactuated and strongly coupled system. For the dynamic analysis, aerodynamic effect of drag, the thrust due to the propellers and external wind fields are considered. The evaluation of the needed thrust for prescribed trajectories gives indications about the type of propellers and actuator characteristics to be installed on the UAV
Bifactorial Pricing Models: Light and Shadows in Correlation Role
No full textIn modern option pricing theory many attempts have been accomplished in order to release some of the traditional assumptions of the Black and Scholes [5]
model. Distinguished in this field are models allowing for stochastic interest rates, as suggested for the first time by Merton [20]. Afterwards, many stochastic interest
rate models to evaluate the price of hybrid securities have been proposed in literature. Most of these are equilibrium pricing models whose parameters are estimated
by means of statistical procedure, requiring a considerable computational burden. The recent financial crisis and the resulting instability of relevant time series may sensibly reduce the reliability of estimated parameters necessary to such models and, consequently, the calibration of the models. In this paper we discuss an original numerical
procedure that can efficiently be adopted to the aim of pricing and the question of the correlation contribution in pricing framework. The procedure accounts
for two sources of risk (the stock price and the spot interest rate) and, by means of an empirical evaluation tries to asses the relative contribution of the correlation component.
The final target is to evaluate the “optimal” computation burden in pricing framework, given scarce dataset We show that the procedure proposed is a valuable
compromise between computational burden and calibration efficiency, mainly because it overcomes difficulties and arbitrary choices in the estimation of the parameters
Obstacle Avoidance System for Unmanned Ground Vehicles by Using Ultrasonic Sensors
No full textArtificial intelligence is the ability of a computer to perform the functions and reasoning typical of the human mind. In its purely informatic aspect, it includes the theory and techniques for the development of algorithms that allow machines to show an intelligent ability and/or perform an intelligent activity, at least in specific areas. In particular, there are automatic learning algorithms based on the same mechanisms that are thought to be the basis of all the cognitive processes developed by the human brain. Such a powerful tool has already started to produce a new class of self-driving vehicles. With the projections of population growth that will increase until the year 2100 up to 11.2 billion, research on innovating agricultural techniques must be continued. In order to improve the efficiency regarding precision agriculture, the use of autonomous agricultural machines must become an important issue. For this reason, it was decided to test the use of the “Neural Network Toolbox” tool already present in MATLAB to design an artificial neural network with supervised learning suitable for classification and pattern recognition by using data collected by an ultrasonic sensor. The idea is to use such a protocol to retrofit kits for agricultural machines already present on the market
Multibody Analysis of Sloshing Effect in a Glass Cylinder Container for Visual Inspection Activities
No full textThis paper addresses the phenomenon of sloshing and the issues that arise during liquid handling at visual inspection stations. The pharmaceutical industry, recently put under pressure by the pandemic, has long adopted modular solutions consisting mainly of robotic islands. This work focuses on a visual inspection island for glass vials and ampules called VRU. This machine uses robotic arms to optimize the inspection process and enables automated control of a wide range of products using image recognition techniques and AI algorithms. However, the handling of containers in the presence of liquids requires special precautions to avoid the occurrence of bubbles inside the fluid that can prevent the cameras from correctly capturing any defects present. The banal solution involves a drastic reduction in the speeds and accelerations to which the liquids are subjected. However, using appropriate techniques makes it possible to achieve performance values similar to those obtainable when manipulating solid materials. The developed algorithms were tested using multibody simulations in the Mathworks Simscape environment and then validated using a six-axis Fanuc robot. In this study, however, the analysis conducted aimed to determine the correlations between trajectories, laws of motion, and sloshing in containers handled at high speed in industrial applications. In this study a multibody model was developed using a CFD analysis. The container consisted of a glass vial for pharmaceutical uses containing a liquid inside. The results obtained from the CFD analysis allowed us to calibrate the multibody model for the next phase of optimization of the laws of motion to be followed by the manipulator
Application of Signal Processing Techniques to the Vibration Analysis of a 3-DoF Structure Under Multiple Excitation Scenarios
No full textStructural Health Monitoring (SHM) techniques are crucial for evaluating the condition of structures, enabling early maintenance interventions, and monitoring factors that could compromise structural integrity. Modal analysis studies the dynamic response of structures when subjected to vibrations, evaluating natural frequencies and vibration modes. This study focuses on detecting and comparing the natural frequencies of a 3-DoF structure under various excitation scenarios, including ambient vibration (in healthy and damaged conditions), two types of transient excitation, and three harmonic excitation variations. Signal processing techniques, specifically Power Spectral Density (PSD) and Continuous Wavelet Transform (CWT), were employed. Each method provides valuable insights into frequency and time-frequency domain analysis. Under ambient vibration excitation, the damaged condition exhibits spectral differences in amplitude and frequency compared to the undamaged state. For the transient excitations, the scalogram images reveal localized energetic differences in frequency components over time, whereas PSD alone cannot observe these behaviors. For the harmonic excitations, PSD provides higher spectral resolution, while CWT adds insight into temporal energy evolution near resonance bands. This study discusses how these analyses provide sensitive features for damage detection applications, as well as the influence of different excitation types on the natural frequencies of the structure
Design of Experiments Approach for Structural Optimization of Urban Air Mobility Vehicles
No full textThe current global context demands the development of new solutions that prioritize energy efficiency, time optimization, safety, and sustainability. Urban transportation is one of the sectors undergoing significant transformation. Pursuing new urban transportation solutions has become increasingly intense, involving research institutions and companies. Considering this context, this study focused on the optimization procedures for designing a new vehicle capable of vertical take-off for urban air mobility applications. This paper reports on the optimization process of a thruster deployment mechanism using statistical techniques. In particular, the authors tested the use of Design of Experiments (DOE) techniques for the optimal design of a structural component of a new vehicle for urban mobility purposes under development at the Applied Mechanics laboratory of the Department of Industrial Engineering of the University of Salerno. For this reason, it was decided that a parametric multibody model would be developed in the Simscape Multibody environment for structural optimization using designed experiment plans to “guide” the designer in the analysis phase and search for an optimal configuration using a minimum number of configurations. Finally, employing FEM analysis, the chosen configuration was validated. This study allowed us to test the use of DOE techniques to design new systems. It allowed us to evaluate different configurations, the static and dynamic behavior, the constraining reactions present in the joints, and the active forces and torques of the actuators, highlighting the correlation between factors that can guide the designer in identifying optimal solutions
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