Adolfo Senatore

Torque Transmissibility Assessment for Automotive Dry-Clutch Engagement

Dry clutches are widely used in conventional and innovative automotive drivelines and represent a key element for automated manual transmissions (AMTs). In practical applications, it is fundamental to model the clutch behavior through its torque transmissibility characteristic, i.e., the relationship between the throwout bearing position (or the pressure applied by the clutch actuator) and the torque transmitted through the clutch during the engagement phase. In this paper, a new model for the torque transmissibility of dry clutches is proposed. It is analyzed how the transmissibility characteristic depends on: friction pads geometry, cushion spring compression, cushion spring load, and slip-speed-dependent friction. Corresponding functions are suitably composed determining the torque transmissibility expression. An experimental procedure for tuning the characteristic parameters is presented. The clutch-torque transmissibility model is tested on a detailed cosimulation model with a typical AMT controller.

Modeling torque transmissibility for automotive dry clutch engagement

The dry clutch is a fundamental component in many automotive drivelines. For instance, the clutch torque transmissibility characteristic severely influences gearshift performance in automated manual transmissions. In this paper a novel model of the torque transmissibility of dry clutches is proposed. The dependence of the transmissibility characteristic on wear, slip speed and friction pads geometry and the influence of the diaphragm spring, the flat spring and the torsional damper springs is taken into account and pointed out. The sensitivity of a clutch engagement control scheme with respect to the clutch characteristic uncertainties is analyzed.

Multiple Constrained MPC Design for Automotive Dry Clutch Engagement

In this paper, a multiple model predictive controller (MPC) is proposed for the management of passenger car start up through dry clutch in automated manual transmission. Based on a high-order dynamic model of powertrain system, the feedback controllers are designed by using the crankshaft angular speed and the clutch disk angular speed as measured variables. Moreover, the MPC is developed to comply with constrains both on the input and on the output. The aim of the controller is to ensure a comfortable lockup and to avoid the stall of the engine as well as to reduce the engagement time. Numerical results show the good performance of the MPC with constrains in overcoming critical operating conditions. Comparisons with similar state-of-the-art works are also shown.

Graphene Oxide Nanosheets as Effective Friction Modifier for Oil Lubricant: Materials, Methods, and Tribological Results

The tribological behaviour of graphene oxide nanosheets in mineral oil was investigated under a wide spectrum of conditions, from boundary and mixed lubrication to elastohydrodynamic regimes. A ball-on-disc setup tribometer has been used to verify the friction reduction due to nanosheets prepared by a modified Hummers method and dispersed in mineral oil. Their good friction and antiwear properties may possibly be attributed to their small structure and extremely thin laminated structure, which offer lower shear stress and prevent interaction between metal interfaces. Furthermore, the results clearly prove that graphene platelets in oil easily form protective film to prevent the direct contact between steel surfaces and, thereby, improve the frictional behaviour of the base oil. This evidence is also related to the frictional coefficient trend in boundary regime.

New 'chimie douce' approach to the synthesis of hybrid nanosheets of MoS2 on CNT and their anti-friction and anti-wear properties.

Hybrid organic-inorganic oleylamine@MoS2-CNT nanocomposites with different compositions were obtained by thermal decomposition of tetrathiomolybdate in the presence of oleylamine and high quality multiwalled carbon nanotubes (CNTs) previously prepared by the CCVD technique. The nanocomposite samples were characterized by the TEM, SEM TG-MS, Raman and XRD techniques and successfully tested as anti-friction and anti-wear additives for grease lubricants.

Modelling the cushion spring characteristic to enhance the automated dry-clutch performance: The temperature effect

The cushion spring plays an important role in an automotive dry-clutch system. It strongly influences the clutch torque transmission from the engine to the driveline through its non-linear load–deflection curve. Therefore, knowledge of the cushion spring compression behaviour is crucial to improve the gearshift performance in an automated manual transmission. Furthermore, the cushion spring compression behaviour is influenced by the temperature because of the frictional heat generation of the clutch facings with the flywheel and the pressure plate surfaces during the engagement phase. In this paper an analysis of the load–deflection curve, taking into account the thermal load to which it is subjected, of a typical passenger car cushion spring is proposed. Six temperatures, in addition to room temperature, were analysed to investigate how the cushion spring load–deflection curve depends on the temperature.

Improving the Engagement Smoothness Through Multi-Variable Frictional Map in Automated Dry Clutch Control

An Automated Manual Transmission (AMT) is directly derived from a manual one through the integration of actuators; then, development and production costs are generally lower than other automatic transmissions, while the reliability and durability are at highest level. For high class sport cars, vehicle dynamic performances and driving quality can be strongly improved with respect to automatic transmissions [1]. AMTs systems are generally constituted by a dry or wet clutch assembly and a multi-speed gearbox, both equipped with electro-mechanical or electro-hydraulic actuators, which are driven by a control unit, the transmission control unit (TCU). The operating modes of AMTs are usually two: semiautomatic or fully automatic. In both cases, after the gear shift command, the TCU manages the shifting steps according to current engine regime, driving conditions and selected program.In this transmission type the quality of the vehicle propulsion as perceived by the driver is largely dependent on the quality of the control strategies. Furthermore, sensitivity analyses on control schemes for AMTs have shown that uncertainties in clutch torque characteristic can severely affect the performance of the clutch engagement: modeling in detail the torque transmitted by the specific clutch architecture is a crucial issue in order to design robust engagement control strategies [2, 3 and 4].This paper aims at investigating the engagement performance of an actuated dry clutch by taking into account the inference of the pressure on the facing materials and the sliding speed. In fact, according to literature outcomes [5], the friction coefficient after a first rising behavior with the sliding speed shows an asymptotic value for a typical clutch facing; the same material exhibits a nearly linear dependence of the friction coefficient on the pressure.The simulations consider: reduced-order dynamic system for simulation of passenger car driveline, control algorithm, experimental maps of the n-D clutch transmission characteristic, and gear shift maneuvers in different operating conditions.The outcome of this analysis could provide valuable issues for designers of automated clutches and control engineers to overcome the well known poor engagement performances of open loop motion strategy of the throwout bearing where cost reason and complexity don’t permit the use of displacement sensor.Copyright

Optimization of manufacturing process effects on brake friction material wear

Manufacturing parameters of brake friction materials have a crucial impact on its friction and wear behavior. The effects of manufacturing parameters on wear have been modeled aiming at the optimization of facing behaviors. The influences of the five most important manufacturing parameters, such as molding pressure, molding time, molding temperature, heat-treatment temperature, and heat-treatment time, have been investigated. Their effects have been investigated on different formulations of the friction material and under different brake interface temperatures. The neuro-genetic optimization model was developed to be able to predict and optimize the effects of manufacturing parameters on the brake friction material wear.

Fundamentals of lubrication and friction of piston ring contact

Abstracts: The piston ring-pack exhibits a complex dynamic behaviour, which includes gas and oil flows, twisting motion of each ring and its influence on ring-liner and ring-groove lubrication and contact, as well as unsteady oil supply. In modern automotive engines, the dynamics result in a significant share of the total friction power loss and plays a crucial role in the piston assembly response in terms of blowby, wear and oil consumption. This chapter illustrates the physics of piston ring lubrication and friction, the main mathematical and computer models and the fundamentals of the ring-pack role. The chapter is completed by future trends and opportunities of research into piston ring modelling and improvements to the frictional behaviour.

Analytical solution for two‐dimensional Reynolds equation for porous journal bearings

Purpose – Aims to explore many aspects of the dynamic behaviour of a rotor on bearings, such as the fluid film force. In order to find in an analytical model an effective solution to provide a more readable description of the interaction between journal and bearing.Design/methodology/approach – The present theoretical analysis is carried out to determine the analytical approximate formulation of the fluid film force of porous finite journal bearings. This paper focuses on an approximate mathematical model for the one‐dimensional lubrication equation about the infinitely long porous journal bearing, while the Warners method is adopted to describe the oil film pressure film in the finite bearing domain.Findings – The proposed model allows a quick analytical determination of the fluid film force for different values of the permeability coefficient, L/D ratio, eccentricity ratio. The results are in good agreement with those achieved by means of the FDM based solution.Originality/value – The results show good...