1,721,136 research outputs found
Editorial: Special issue "automotive tribology"
No full textThe automotive industry faces new challenges and fast technological changes [...
Influence of driving cycles on Euro-3 Scooter emission levels
No full textThis study derives from the need to evaluate the impact on the urban air quality of two-wheeler vehicular class. Mopeds and motorcycles, in fact, are increasingly used in recent years, representing a great share of motor-powered vehicles in urban environment. This paper is finalized at the examination of the emissions of the last generation motorcycles, contributing broadly to extend knowledge of two- wheeler emission behavior, with reference to cold and hot operating conditions. For this aim, an experimental investigation was performed on a medium-size motorcycle belonging to the Euro-3 statutory category, evaluating the exhaust emissions of regulated pollutants. This scooter was tested on a dynamometer bench both on a type approval test cycle and on real-world test cycles in order to study the influence of driving cycles on the emission levels. The statistical processing results of the experimental data were compared with recent emission models for estimating emissions from road traffic
Riduzione dello stress termico in una frizione a secco con l’ausilio del motore elettrico
No full textThermal Compensation Control Strategy in Automated Dry Clutch Engagement Dynamics and Launch Manoeuvre
No full textRepeated engagements in dry clutch systems could yield remarkable increase of clutch disk temperature. In dry clutch based transmissions like Automated Manual Transmissions and Dual Clutch Transmissions the overheating leads to poor control of gearshift quality due to unpredictable and fast change of frictional characteristic. Even permanent damage of clutch facings may occur. Under this light, this paper focusing on thermal effects to improve control performances and prevent uncomfortable engagements. To this aim, detailed analyses of dry clutch architecture have been carried out to understand the main phenomena which affect the clutch torque transmissibility. Moreover, a lumped thermal model has been developed to predict both the disk surface and cushion spring temperature in real-time environment. To validate the proposed thermal model, a non-linear least squares method has been used by comparing simulations with finite element results. A control strategy based on model predictive control and thermal compensation effects has been proposed to simulate vehicle launch manoeuvres in flat and up-hill road conditions with low and high initial clutch temperature as well. Finally, the proposed control approach has been compared with classic PI control strategy to prove its effectiveness
Sliding Mode Control design for EOD robot manipulator and multiphysic analysis
No full textThis paper presents a focus on the dynamic behaviour and the control strategies for an Explosive Ordnance Disposal (EOD) robot. The designed controllers are of two types: PI (Proportional Integral) and SMC (Sliding Mode Control). A CAD-based approach was used to extrapolate information regarding the dynamics of the system and obtaining optimal performance from the second controller. The flexibility of the manipulator's last link was also considered. Three different analyses were carried out. In the first, where the flexibility of the last link has been neglected, all motors are controlled by the PI system. In the second, the flexibility of the third link is taken into account without changing the type of control system. In the third, the control system used is SMC. The obtained results show that the robot is able to carry out the picking and transport task and that the best performer control in SMC type. Moreover, the state of deformation and stress evaluated are not critical for the analyzed component
Modeling and Simulation of a Wave Energy Converter: Multibody System Coupled to Fluid-Film Lubrication Model and Thermal Analysis
No full textSea wave energy is being increasingly regarded as one of the most promising sources of renewable energy. This paper deals with the modeling and simulation of an onshore wave energy converter system designed by UMBRA GROUP SpA. Several topics are addressed. Starting from the multibody modeling strategy, this paper delves more deeply into the mechanical efficiency evaluation of the ball-screw in the elastohydrodynamic lubrication regime, the core of the energy conversion process, as well as the thermal characterization of the power take-off module, based on the lumped-parameter and finite element method models. High values of ball-screw indirect efficiency have been observed, ranging from 73% to 97%; these results appear even more encouraging when compared to the performance of alternative energy-consuming technologies. Thermal analysis, on the other hand, provided a maximum temperature increase of 40 °C, allowing for the aversion of any structural collapse and the realistic identification of the lubrication regime, which turned out to be mostly mixed. Finally, an inverse multibody dynamic analysis is performed, and the most interesting simulation results are collected to prove the effectiveness of the proposed approach
Intelligent Control Strategy for Electric Motor Management to Improve Dry-Clutch Performance in Mild Hybrid Vehicles
No full textThermal degradation is a relevant issue in dry clutch transmissions such as Dual Clutch Transmissions and Automated Manual Transmissions. This occurs if numerous engagements are performed in short time or during up-hill start up manoeuvres. As a consequence of clutch overheating there are: poor control performances during the gearshift phase, resulting from fast and unforeseeable variation of frictional behavior, and reduced clutch lifespan. A solution could be exploit the small electric motor introduced in Mild-Hybrid vehicles to lessen air pollutant emissions and improve fuel economy. The main target of this manuscript is to highlight the electric motor operation to assist vehicle longitudinal dynamics and minimize clutch temperature rise
Real-time identification of dry-clutch frictional torque in automated transmissions at launch condition
No full textHelical Gear Pump: A Comparison between a Lumped Parameter and a Computational Fluid Dynamics-Based Approaches
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