1,721,056 research outputs found
Caso limite di Grashof del quadrilatero articolato piano e terne pitagoriche
No full textNel presente lavoro si studia un semplice problema di sintesi cinematica
di un quadrilatero articolato piano. Dopo aver classificato il quadrilatero in base
ai tradizionali approcci presenti in letteratura, se ne opera la sintesi cinematica
e, successivamente, si trovano le soluzioni del problema di sintesi nel caso in cui
le lunghezze dei membri del quadrilatero siano numeri interi (positivi), mostrando
che sono correlate con le terne pitagoriche primitive. Avere a disposizione delle
soluzioni con lunghezze intere consente un vantaggio non trascurabile quando si
vuole procedere ad una prima sintesi di massima del meccanismo imponendo alcune
proporzioni desiderate tra le lunghezze dei membri. Ciò è di un certo rilievo laddove
le proporzioni e le forme costituiscono un aspetto rilevante, come ad esempio nel
campo dell’interior design o del design in generale
Experimental vibration analysis of an automatic machine for plastic cap assembly.
No full textThe case study presented in this paper concerns vibration measurements performed on an industrial automatic machine for assembling plastic caps. The final purpose of the activity is increasing the machine working speed of 50% (and thus the productivity), by making only limited modifications to the current machine design. Since elastodynamic issues may occur for operation at higher working velocity, an experimental campaign was carried out for assessing the vibrations characterizing the machine functioning at different regimes. The investigation permitted to identify the functional groups exhibiting significant elastodynamic phenomena induced by the speed increment. The results concerning two of these groups, namely a unit for the orientation of the parts to be assembled and a power transmission chain, are presented and discussed
Integration of flexible multibody dynamics and virtual commissioning simulations of a machine tool
No full textAlgorithm for the static balancing of serial and parallel mechanisms combining counterweights and springs: Generation, assessment and ranking of effective design variants
Full text linkStatic balancing through passive devices is a suitable strategy to reduce motor loads for numerous applications in the automation and robotics fields. Many known methods require initially defining which balancing elements to install, thus possibly limiting the compensation effectiveness, since potentially optimal solutions may be neglected. This work presents an approach to statically balance linkages characterized by open and/or closed kinematic chains. The proposed algorithm searches for possible balanced variants of the mechanism that can be arranged by installing combinations of counterweights and springs, without auxiliary linkages. If solutions are found, the corresponding balancing parameters are tuned for optimizing the mechanism energy consumption, by considering the mechanism dynamics when performing its operational tasks. Actual benefits and drawbacks of the variants are assessed through quantitative criteria. The corresponding performance indicators are proposed as a guideline for designers to identify the most convenient balancing solutions. The implemented procedure is general and suitable to study any mechanism admitting closed-form solutions for its forward kinematics. A case study concerning an industrial palletizing robot is reported as an example of application. Overload issues affecting the robot actuators are solved through gravity compensation. The results achieved for the industrial problem prove the procedure effectiveness
Component mode selection in flexible multibody dynamics with application to cranktrain modelling.
No full textThis paper discusses the development of a multibody model of a Ducati L-twin engine cranktrain, with an emphasis on component flexibility and model reduction. In fact, the main components in the system are modelled as flexible: starting from a Finite Element description of such components, the standard Craig-Bampton technique is employed to reduce the model order. The Effective Interface Mass measure of dynamic importance is used to rank fixed-interface normal modes based upon their contribution to loads at the substructure interface; modes to retain are then selected according to such modal ordering scheme. In order to assess the performance of the adopted modal selection criterion, tests are performed on both the connecting rod model, by means of dynamic linear simulations in time and frequency domain, and the
complete cranktrain assembly, through nonlinear multibody analyses. Results concerning both accuracy and efficiency are presented and discussed
Optimal static balancing of a spatial palletizing robot.
No full textStatic balancing is often used in industrial applications in order to reduce the actuator efforts required during the machine operations. Literature offers a number of methods to study static balancing and to define positions and features of the balancing devices that are commonly used to achieve gravity compensation, i.e. counterweights, springs, hydro/pneumatic cylinders, and/or auxiliary parallelograms. This work deals with the static balancing of a commercial spatial manipulator, primarily conceived for palletizing tasks with a maximum payload of 150 kg. Since the robot has a hybrid architecture that includes closed kinematic chains, common balancing methods for serial manipulators are not suitable and new solutions must be developed. The paper proposes a number of different balancing solutions which include counterweights and springs, whose characteristics and positions are determined by means of an optimization algorithm. The effectiveness of each solution is investigated and the corresponding feasibility is discussed
Characterization of the Dynamic Response of a Fuel Cell Through EMA and Vibration Testing
No full textAdvancements in fuel cell (FC) technological capabilities, particularly in operational efficiency, energy density, and systemic integration, have established these systems as critical enablers for next-generation vehicles. Vibrationinduced effects on FCs within such applications represent a primary factor impacting system integration fidelity, operational reliability, and electrochemical stability, and therefore they must be carefully assessed. This study examines a lightweight FC architecture designed for unmanned aerial vehicles (UAV) deployment under vibrational loading conditions, taken as a starting point of the research. Experimental modal analysis (EMA) was conducted to characterize mode shapes, associated natural frequencies, and damping ratios in free-free boundary conditions. These results may enable accurate modelling and simulation of such devices and may be exploited for bigger size FC suitable for automotive applications. Forced vibration testing investigated the system vibrational response to sinusoidal and random excitation profiles for a possible mounting configuration of the FC, also in relation to the FC orientation. The EMA could identify torsional modes, whereas the forced vibration measurements permitted to characterize both the in-plane and out-of-plane dynamic response of the FC, as well as to test the analysis tools. These results are deemed a significant reference for deeper studies on FCs for automotive applications
Experimental vibration analysis of a rotary transfer machine for the manufacture of lock components
No full textThis study deals with vibrations in machine tools featuring rotary transfer architecture. The machine tool manufacturer aims at two long-term achievements, namely developing a reliable virtual testing tool to aid the design process of new products, and implementing a real-time system for condition monitoring and diagnostics of the cutting tool and the machining units to be equipped on-board. A seven-station rotary transfer machine with multi-spindle CNC machining units is investigated as a starting point of the research. An experimental campaign is carried out to assess the machinery vibration response. Several different experiments are conducted to estimate the modal parameters of the machine as well as to identify the elastodynamic effects induced by the nominal working cycle and by each machining operation. The result analysis permitted to identify potentially critical issues and to define the corresponding strategies to overcome them. In particular, limited modifications of the machining parameters and a partial redesign of just one machine component are suggested
Braking Torque Estimation Through Machine Learning Algorithms
No full textMotoGP class motorcycles rely on carbon braking system to cope with their incredible acceleration capability and high speed. Hence, assessing the torque generated by the front discs is a key to improve the vehicle performance. As direct measurement of the braking torque is not allowed during races, its value may be estimated through a physical model, using as inputs the brake fluid pressure (monitored on board), the braking system geometry and the friction coefficient (μ). However, the results obtained with this method are highly limited by the knowledge of the instantaneous friction coefficient between the disc rotor and the pads. Since the value of μ is a highly nonlinear function of many variables (namely temperature, pressure and angular velocity of the disc), an analytical model appears impractical to establish. This work aims to implement an innovative algorithm, based on machine learning, for determining μ from the signals regularly available in races, to enable accurate breaking torque computation. The proposed method consists of two main tools. An artificial neural network (ANN) is developed to approximate the unknown function that relates the input variables to μ, while a Kalman filter (KF) is implemented to estimate the real temperature distribution on the disc surface that constitutes one of the most important ANN inputs. The proposed algorithm has been successfully validated with real data collected from extensive tests in racetracks, with a special sensor setup
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