948 research outputs found
Spinoza e Bruno. Per la storia di una questione storiografica.
No full textIl volume è a cura di Daniela Bostrenghi e Cristina Santinelli; introduzione di Cristina Santinelli.
Il saggio si propone di indagare dal punto di vista critico e storiografico i rapporti tra la filosofia di Spinoza e quella di Giordano Bruno
A Florentine family in crisis: the Strozzi in the fifteenth century.
No full textPhDIn 1434 the Strozzi lineage had held a leading position in
Florentine society and government for at least one hundred and fifty
years, and was one of the largest and wealthiest of the city's
patrician lineages. The records of the catasto of 1427 and of the
scrutiny of 1433 are used to give a profile of the dominant social,
economic and political position of the Strozzi before the advent of
Medicean dominance. Their record of electoral success, and the
political and cultural leadership of influential and respected men
such as Palla di Nofri and Matteo di Simone, with other factors, put
the Strozzi amongst the greatest enemies of the victorious Medicean
regime of late 1434. The effects of political opposition and exile
on the lineage are examined both directly, through records of office-holding,
and indirectly through such indicators as marriage alliances
and household wealth. The two most prominent lines of the Strozzi
were exiled after 1434. Palla di Nofri's life and preoccupations in
his Paduan exile are examined, together with the lives of his sons;
none of these Strozzi ever returned to Florence, pursued as they were
by the enmity of the Medicean regime. The very different careers of
Filippo di Matteo and his brother Lorenzo are also examined: how they
succeeded in founding a lucrative bank in Naples, and in returning to
Florence to 'rebuild' (rifare) the position of the Strozzi lineage
there. The final decades of the century saw the Strozzi in an
economically more secure position, due substantially to the efforts
of Filippo. Except for a very small number of its members admitted
into the regime, most of the lineage is here shown to have remained
excluded from significant political office until after the fall of
the Medici regime in 1494
Real Time MEMS-Based Joint Friction Identification for Enhanced Dynamic Performance in Robotic Applications
No full textThe mechatronic design approach to robotics deploys, inter alia, widely available mechanical design engineering tools that, together with standard production techniques, allow the accurate quantification of the system’s mass properties. While this enables the synthesis of model-based centralized controllers, friction still limits the achievable dynamic performances, as its prediction at the design stage is hampered by complex dependencies on loads, temperature, wear, and lubrication. Further uncertainties affecting mechatronic devices stem from the actuation systems, whose parameters are specified by the manufacturer with relatively loose accuracy. These challenges are addressed here through a method based on MEMS IMUs for the real-time estimation of both friction effects and uncertain actuator parameters. The resulting model, inclusive of the frictionless dynamics, is applied in a closed loop to improve the control performance. An experimental comparison with decentralized and non-adaptive regulators highlights severalfold reductions in tracking errors; the ability to track temperature-dependent friction variations is also shown. From this work, it may be concluded that the use of MEMS sensors, together with identification and adaptive control algorithms, sensibly increases the dynamic performance of robotic systems. The real-time properties of the method also enable future investigations into topics such as MEMS-based diagnostics and predictive maintenance
A systematic management and control methodology for high energy saving in applications equipped with hydraulic servo-axes
No full textA systematic methodology for the real-time improvement of the overall efficiency of applications using hydraulic servo-axes is presented. The proposed methodology introduces three modules: a hydraulic actuator load estimator, a hydraulic energy optimizer and a controlled hydraulic power supply; these are discussed at the theoretical and application level. The proposed approach reduces the power losses across the main elements of the hydraulic circuit, leading to high energy savings and introducing a new guideline on managing and controlling the servo hydraulic actuator. The methodology is applicable to any application using hydraulic servo-axis systems, and therefore it is not tailored to a particular field. Its performances have been evaluated in different industrial case studies (a blanking press, a drawing press and a die-casting plant) through numerical simulations. Conspicuous energy savings, ranging between 59% and 88%, have been obtained in simulation, suggesting that a significant carbon footprint reduction for energy-intensive hydraulic machinery is achievable in a wide range of applications
Endoscopic ultrasound-guided single-incision with needle knife and deep tissue biopsy for the diagnosis of gastric subepithelial tumor
No full textCo-simulation of Impedance and Hybrid Motion-Force Control Strategies on a 4-DOF 5R Parallel Manipulator
No full textImpedance and hybrid motion-force control systems allow robots to perform complex manipulation tasks in which both force and position should be simultaneously regulated. In contrast to solutions based on passive compliant elements, active control allows adaptation to varied working conditions, through variations of the control system parameters. The evaluation of force control strategies is typically performed experimentally, due to the difficulty of accurately modelling at once different phenomena like contact dynamics, mechanical compliances, measurement noise and delays that affect the actual performance of controller, whose synthesis is necessarily based on simplifying assumptions. The use of co-simulation techniques constitutes however an alternative to experimental tests, and allow the safe and effective analysis of the effects of non-idealities not foreseen at the design stage. This work, therefore, investigates the feasibility of contour tracking of unknown planar profiles with a 4-DOF parallel manipulator using Simulink and MSC Adams co-simulations. The results allow a first selection of the most effective control strategies, and suggest that, prior to implementation on the physical prototype of the robot, friction contact compensation should be introduced in order to accurately track velocities and forces also in the presence of significant tangential disturbances
Experimental Investigation on a Power Supply Control System for Hydraulic Actuators
No full textHydraulics is a technology widely used whenever high power is required with relatively small dimensions of the components. However, despite the high power density that characterizes the hydraulic components, they are intrinsically dissipative due to pressure drops across them. One of the possible adoptable solutions to increase the efficiency of the system is to control the power supply at the aim to tailor the generated power to the load demand. Many of the proposed solutions retrievable in literature lead to significant modifications of the hydraulic circuit, and are not of general validity for other kinds of systems. The present paper focuses exactly on a new kind of power supply control system, with a low impact on a hydraulic plant, and applicable to different kinds of systems. It is based on the regulation of the supply pressure by means of a servo valve. This new power supply control system is analysed through preliminary experimental activities conducted on a test rig, where the pressure of the fluid within a constant volume is controlled. Firstly, the bandwidth of the transfer function between the servo valve command and the supply pressure is evaluated. Secondly, a closed loop control of the supply pressure is realized, considering a pressure set-point drawn from a real case, already studied by the authors in a previous work. The experimental results show that the system is able to follow the set-point with a very small error. At the same time, a system model where the fluid is considered incompressible has been set-up. The relevant transfer function obtained shows remarkable differences with respect to the experimental one. Hence, the model needs to be reviewed including other effects, like fluid's compressibility, at the moment neglected. Besides the model improvement, authors have been planning other experimental activities in different conditions to confirm the preliminary results obtained
Parallel Kinematics Manipulators for Pick and Place of Moving Objects Using 3D Perception: Development of a Test Bench
No full textInterest in increasing the efficiency of manufacturing processes has led to a wide research effort focused on pick- and-place of moving objects. This topic presents a number of difficulties and consequently areas for research due to the need to integrate and optimize both the visual perception system, the image processing algorithm, and the robot control system. In the literature, many experimental efforts regarding new proposals to improve this process are carried out using anthropomorphic manipulators. The authors’ interest is instead to develop a testbed in order to investigate the various issues concerning dynamic pick-and-place, using a parallel kinematics manipulator. In fact, parallel kinematics manipulators are widely used in industry for high-speed pick-and-place tasks due to their inherent stiffness and dynamic performance. In this paper, a 4-degree-of-freedom 5R parallel kinematics robot will be integrated with a 3D camera for tracking moving objects. The manipulator and 3D camera will be presented, and then the software and hardware architecture of the testbed, resulting from the integration of the two systems, will be described. The object tracking algorithm used will be described, and analysis regarding its computational performance will be shown. Finally, considerations about the feasibility of integrating the two systems for dynamic pick-and-place will be drawn, deriving the future activities that are intended to be done
Vues présentes sur le celtique cisalpin
No full textPresent views on Cisalpine Celtic.
During the last twenty years, the knowledge of Lepontic and of Italian Gaulish has been notably enriched by very important finds, and also by numerous studies. The author proposes a synthesis of all new linguistical and cultural data provided by epigraphy in this particular resort.Dans les vingt dernières années la connaissance du lépontique et du gaulois d’Italie a été notablement enrichie par certaines trouvailles fort importantes ainsi que par de nombreuses études. Tableau synthétique des nouvelles données linguistiques et culturelles apportées par l’épigraphie de ce domaine.Motta Filippo. Vues présentes sur le celtique cisalpin. In: Etudes Celtiques, vol. 29, 1992. Actes du IXe congrès international d'études celtiques. Paris, 7-12 juillet 1991. Deuxième partie : Linguistique, littératures. pp. 311-318
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