1,721,012 research outputs found
PREFACE FOR THE SPECIAL ISSUE OF THE INTERNATIONAL JOURNAL OF MECHANICS AND CONTROL (JOMAC) DEDICATED TO THE 4TH IFTOMM ITALY CONFERENCE
No full textA simplified model of a multi-jointed mechanical finger calibrated with experimental data by vision system
No full textThe development of suitable models for mechanical fingers, whether they are part of prosthetic device or of a robotic hand, is a powerful tool to predict the behaviour of their components since the early stages of design, especially for underactuated mechanisms. Experimental data can improve the reliability of such models and promote their application to build proper control strategies especially for prosthetic hands. Here, we have developed a multi-jointed model of a mechanical finger. The finger is part of the Federica hand: an underactuated mechanical hand that was conceived for prosthetic purpose. The model accounts for friction phenomena in the finger and it is tuned with experimental data acquired through a digital image correlation device. The model allowed us to write kinematics relations of the phalanges and evaluate finger configurations in relation to the closure velocity. Moreover, it was possible to estimate the tendon force and the work analysis occurring during the closure tasks, both in free mode and in presence of objects
Nonlinear estimation of the Bouc-Wen model with parameter boundaries: Application to seismic isolators
No full textThe Bouc-Wen model is one of the most widely used parametric models of hysteresis. The exactness of the Bouc-Wen model depends on the correctness of the model parameters that are subjected to bound constraints in accordance with their physical meaning. Constraints and nonlinearities of the model introduce a complexity for the parameter estimation. In this paper, a constrained unscented Kalman filter (CUKF) is proposed in order to identify the hysteresis model parameters in a robust and reliable way. The adopted parameter estimator has been compared with the well-known extended Kalman filter (EKF) that is often used for nonlinear system identification. The effectiveness of the proposed approach has been verified by numerical simulations and experimental tests. In particular, for the experimental verification of the CUKF, the Bouc-Wen model has been adopted to describe the hysteretic shear behaviour of a seismic isolator. The results show that the CUKF provides better parameter identification than the EKF also taking into account parameter boundaries
Vision based techniques for the experimental characterization of a prosthetic finger model
No full textSeveral prototypes of mechanical fingers composing anthropomorphic prosthetic hands have been developed using underactuated mechanisms. These mechanisms require specific experimental procedure to measure their properties. Due to their low weight, the addition of further sensors for measurement purposes could modify the trajectory of the single parts and the overall prosthetic device behaviour. Vision system methods represent a route to overcome these drawbacks. In this study, an experimental methodology to acquire the dynamics of an underactuated prosthetic finger is presented due to the employment of a vision-based technique, the Digital Image Correlation. The experimental characterization AIDS the development of a dynamical model of the finger behaviour
Multibody Model for the Design of a Rover for Agricultural Applications: A Preliminary Study
No full textThe employment of vehicles such as rovers equipped with automictic and robotic systems in agriculture is an emerging field. The development of suitable simulation models can aid in the design and testing of agricultural rovers before prototyping. Here, we propose a simulation test rig based on a multibody model to investigate the main issues connected with agricultural rover designs. The results of the simulations show significant differences between the two structures, especially regarding the energy savings, which is a key aspect for the applicability of a rover in field operations. The modular structure of the proposed simulation model can be easily adapted to other vehicle structures
Vibrational analysis to detect cavitation phenomena in a directional spool valve
No full textThe study of the cavitation phenomenon in directional spool valves has been widely addressed through different types of analysis, since the implosion of the bubbles compromises the operation of the system and it causes progressive damage up to the emergence of cracks which could lead to an early breakdown of the system. In this work, the cavitation phenomenon has been studied trough vibrational analysis of accelerometric signals acquired on a directional spool valve. The accelerometric signals have been processed by tools of statistical analysis able to identify three physical phenomena occurring in valve proximity: absence of cavitation, starting cavitation phenomenon and strong cavitation phenomenon. It has been demonstrated that some statistical indices are able to differentiate well the behaviour of the valve in various cavitation states
Protesi di mano sottoattuata a dita bloccabili azionabile mediante sensore piezoresistivo a forma di calotta sferica
No full textL’invenzione fa riferimento al campo della tecnica comprendente le protesi di arto superiore del tipo cinematico ovvero dotate di meccanismi che consentono di ottenere il movimento di alcune, o di tutte, le dita necessarie alla presa di un oggetto ed azionabili meccanicamente o elettricamente. In particolare, il trovato oggetto della presente invenzione riguarda una protesi di mano sottoattuata a dita bloccabili azionabile mediante sensore piezoresistivo a forma di calotta sferica. La presente invenzione mira a sviluppare una protesi di mano dotata di meccanismo di azionamento sottoattuato, economica e dotata di un sistema elettronico di azionamento affidabile che non necessiti il contatto elettrico con l’utilizzatore
Comparison of linear methodologies and not for the evaluation of the vibrational morphodynamics of a pair of gears in different tribological conditions
No full textThe gear wheels are the most common mechanism for the transmission of the torque between two organs. The tribological conditions can compromise both their performance and lifetime. Vibration analysis is a valid tool for the assessment of the health of a mechanical system. The following work illustrates a non-linear methodology for evaluating the vibrational dynamics of a single pair of gears, under different tribological conditions. The proposed methodology highlights the presence of damage 011 the surface of the teeth of the gear pair and evaluates effect 011 micro-vibratory dynamics due to different lubrication and rotation regimes. Once the vibratory dynamics features of the structure are known, a statistical model has been developed capable of classifying the different tribological regimes
Spring-Loaded Rocker-Bogie Suspension for Six Wheeled Rovers
No full textRovers equipped with articulated rocker-bogie suspension have aroused great interest after the explorations on Mars and their interest has also shifted to different types of terrestrial applications such as in the field of agriculture, rescue, etc. In this paper after analysing the distribution of loads on the wheels in different operating conditions, the possibility of equipping the passive hinge, that connects the rocker with the bogie, with a torsional spring with adjustable preload, is evaluated. The introduction of the spring has the aim of modifying the load on the wheels to favour the beginning of the overcoming of a step obstacle having height greater than the wheel radius
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