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Technical Paper

Sensitivity Analysis of the Design Parameters of a Dual-Clutch Transmission Focused on NVH Performance

2016-04-05
2016-01-1127
This paper presents a methodology for the assessment of the NVH (noise vibration and harshness) performance of Dual Clutch Transmissions (DCTs) depending on some transmission design parameters, e.g. torsional backlash in the synchronizers or clutch disc moment of inertia, during low speed maneuvers. A 21-DOFs nonlinear dynamic model of a C-segment passenger car equipped with a DCT is used to simulate the torsional behavior of the driveline and to estimate the forces at the bearings. The impacts between the teeth of two engaging components, e.g. gears and synchronizers, generate impulses in the forces, thus loading the bearings with force time-history characterized by rich frequency content. A broadband excitation is therefore applied to the gearbox case, generating noise and vibration issues.
Technical Paper

Linear Approach to ESP Control Logic Design

2006-04-03
2006-01-1017
An Electronic Stability Program (ESP) control logic is designed. It is devoted to stabilize vehicle during cornering maneuvers. The aim of the activity is to obtain a feed forward (FF) control structure, capable of better performance than a previously developed closed loop one. The efficiency of ESP intervention is determined observing yaw rate peak reduction and oscillation damping time during step steer maneuver, together with vehicle side slip angle containment and longitudinal speed loss. A single track vehicle model is used to obtain two transfer functions describing vehicle and active system behavior. A third transfer function is derived from active vehicle frequency response that is the designer's target. The interaction between the transfer functions permits to design a feed forward control logic, which is then merged in a closed loop control structure in order to ensure fail safe conditions and control robustness.
Technical Paper

Integrated Active and Passive Systems for a Side Impact Scenario

2013-04-08
2013-01-1162
The paper presents a simulation methodology created to support an integrated safety system development process which was tested for the side impact collision load case. The methodology is based on the coupled and complementary use of two software packages: PreScan and Madymo. PreScan was utilized for designing two traffic scenarios and the sensing and control systems for the side collision recognition, while Madymo was utilized for assessing the effects of pre-crash deployment of thorax airbag. The collision conditions from the scenarios were used as input to define a Madymo side collision model of the host vehicle and to investigate and optimize several airbag deployment parameters: pre-crash deployment time, airbag permeability, vent hole size and vent hole opening time.
Technical Paper

Hardware-In-the-Loop Testing of Automotive Control Systems

2006-02-14
2006-01-1962
The paper deals with the methodology implemented by Magneti Marelli and Politecnico di Torino Vehicle Dynamics Research group to develop and verify the software of active chassis and powertrain control systems through a Hardware-In-the-Loop automated procedure. It is a general procedure which can be adopted for all the active chassis control systems, not only for their development but also for the verification of their reliability. The steps of the procedure are described in the first part of the paper. The specific application on which this paper is focused concerns robotized gearboxes.
Technical Paper

Experimental-numerical correlation of a multi-body model for comfort analysis of an heavy truck

2020-04-14
2020-01-0768
In automotive market, today more than in the past, it is very important to reduce time to market and, mostly, developing costs before the final production start. Ideally, bench and the on-road tests can be replaced by multi-body studies because virtual approach guarantees test conditions very close to reality and it is able to exactly replicate the standard procedures. Approval authorities are starting to look at simulations to release homologation certificates. Therefore, today, it is essential to create very reliable models, able to forecast the vehicle behavior on every road condition (including uneven surfaces). The aim of this study is to build a reliable multi-body model of a heavy commercial vehicle and to correlate experimental and numerical data related to comfort analysis for validation purposes. Experimental results are recorded during tests carried out at different speeds and loading conditions on a Belgian blocks track.
Technical Paper

Experimental Test of Vehicle Longitudinal Velocity and Road Frictim Estimation for ABS System

2009-04-20
2009-01-0428
Antilock Braking System (ABS) is designed to prevent wheels from locking, in order to enhance vehicle directional stability during braking manoeuvres. Basically, ABS closed-loop control logic uses tyres slip as control variable. Slip is estimated by comparing vehicle reference speed with the angular speed of each wheel. Thus it is crucial to correctly estimate the longitudinal vehicle speed, in order to get a control system capable of good performance. The control is also affected by road condition; since vehicles are not equipped with sensors able to measure the tyre/road friction coefficient, an other estimation has to be performed. The paper presents an algorithm for the estimation of longitudinal speed, based on the measurements of the four wheel angular speed. A method to assess the road friction, commonly known as “learning phase” is also described: it is carried out during the early stage of the active control intervention and relies on the wheel rotation sensors as well.
Technical Paper

Enhancing Transmission NVH Performance through Powertrain Control Integration with Active Braking System

2017-06-05
2017-01-1778
This paper explores the potentiality of reducing noise and vibration of a vehicle transmission thanks to powertrain control integration with active braking. Due to external disturbances, coming from the driver, e.g. during tip-in / tip-out maneuvers, or from the road, e.g. crossing a speed bump or driving on a rough road, the torsional backlashes between transmission rotating components (gears, synchronizers, splines, CV joints), may lead to NVH issues known as clonk. This study initially focuses on the positive effect on transmission NVH performance of a concurrent application of a braking torque at the driving wheels and of an engine torque increase during these maneuvers; then a powertrain/brake integrated control strategy is proposed. The braking system is activated in advance with respect to the perturbation and it is deactivated immediately after to minimize losses.
Technical Paper

Dual-mass flywheel with torque limiter: an effective solution for overtorque suppression in automotive transmission

2020-04-14
2020-01-1016
During some critical maneuvers, transmission systems using Dual Mass Flywheel (DMF) may experience overtorques, which could possibly lead to structural damages of the transmission components. A dual mass flywheel is essentially composed by two inertias: a primary mass connected to the engine and a secondary mass to the clutch. The torque delivered by the engine is transmitted through a drive plate and arc springs, the latter absorbing the torsional oscillations coming from internal combustion engine. This paper investigates overtorque issues that affect DMFs in automotive transmission and proposes a solution based on a torque limiter, consisting in a friction clutch inserted between the two masses. This device limits the maximum torque to a specific slipping value. Experimental analysis on a dedicated bench tested the durability of different friction pads and the variation of the slipping torque with time.
Technical Paper

Dual Clutch Transmission Vibrations during Gear Shift: A Simulation-Based Approach for Clunking Noise Assessment

2019-06-05
2019-01-1553
A novel methodology, for the assessment of Dual Clutch Transmission vibrations during gear shifts, is proposed in this paper. It is based on the capability to predict through numerical simulation a typical dynamic quantity used to objectively evaluate the vibrational behavior of a gearbox during experimental tests, i.e. the acceleration of a point on the external surface of the gearbox housing. To achieve this result, a two-step approach is proposed: an accurate simulation of the internal transmission dynamics and an offline uncoupled computation of the gearbox housing acceleration from the output of the simulation. The first step required the definition of a suitable nonlinear lumped parameter model of the car equipped with a DCT that was implemented in Amesim software.
Technical Paper

Block-oriented Models of Torque Gap Filler Devices for AMT Transmissions

2008-04-14
2008-01-0631
Vehicles equipped with Automated Manual Transmissions (AMT) for gear shift control show many advantages in terms of reduction of fuel consumption and improvement of driving comfort and shifting quality. In order to increase both performance and efficiency, an important target is focused on the minimization of the typical torque interruption during the gear shift, especially in front of the conventional automatic transmission. Recently, AMT are proposed to be connected with planetary gears and friction brakes, in order to reduce the torque gap during the gear change process. This paper is focused on a block-oriented simulation methodology developed in Matlab/Simulink/Stateflow® environment, able to simulate the performance of a complete FWD powertrain and in particular to predict dynamic performance and overall efficiency of the AMT with innovative Torque Gap Filler devices (TGF).
Technical Paper

Base Model Simulator (BMS) - A Vehicle Dynamics Model to Evaluate Chassis Control Systems Performance

2005-04-11
2005-01-0401
Chassis Control Systems development methodology is nowadays strongly based on analyzing performance by using PC vehicle dynamics simulation. Generally, the overall design, test bench and road validation process is continuously accompanied by simulation. The Base Model Simulator was developed by the Vehicle Dynamics Group at the Department of Mechanics of Politecnico di Torino both to satisfy this requirement and for educational purposes. It considers a complete vehicle dynamics mathematical model, including driver, powertrain, driveline, vehicle body, suspensions, steering system, brakes, tires. The Base Model Simulator takes in account the suspensions system elastokinematics, including, for example, automatic computation of camber variation during the vehicle roll motions. Tire model considered are either Pacejka's models or experimental data.
Journal Article

A Theoretical Investigation of the Influence of Powertrain Mounts on Transmission Torsional Dynamics

2017-03-28
2017-01-1124
This paper investigates the effect of the powertrain mounting system on the linear and nonlinear torsional dynamical behaviour of a transmission system. To this aim, two dynamic models, one with rigid mounts and the other with flexible mounts, are presented and compared: the first model considers only the torsional dynamics of transmission and driveline, while the second model includes also a 3 degrees-of-freedom powertrain block. The mechanical coupling and interaction between the powertrain block and transmission system is discussed and formulated. These models are then analyzed in terms of vibrational mode shapes, natural frequencies and Frequency Response Functions (FRFs); a sensitivity analysis of the main transmission parameters, e.g. the gear ratio, is also presented.
Technical Paper

A Smart Measuring System for Vehicle Dynamics Testing

2020-04-14
2020-01-1066
A fast measurement of the car handling performance is highly desirable to easily compare and assess different car setup, e.g. tires size and supplier, suspension settings, etc. Instead of the expensive professional equipment normally used by car manufacturers for vehicle testing, the authors propose a low cost solution that is nevertheless accurate enough for comparative evaluations. The paper presents a novel measuring system for vehicle dynamics analysis, which is based uniquely on the sensors embedded in a smartphone and completely independent on the signals available through vehicle CAN bus. Data from tri-axial accelerometer, gyroscope, GPS and camera are jointly used to compute the typical quantities analyzed in vehicle dynamics applications.
Technical Paper

A Prototype Vehicle for Powertrain and Chassis Control System Tests

2011-06-09
2011-37-0028
A prototype vehicle (PV) is equipped to test powertrain and active chassis systems with innovative control strategies for safety and energy saving. Additional sensors installed on-board allow the measurement and estimation of new information useful to the vehicle dynamic control. The PV was based on a serial production passenger car with Electronic Stability Control (ESC). Testing activities on Controller Area Network (CAN) and ESC Electronic Control Unit (ECU) are carried out to compare the vehicle dynamic performance obtainable using serial production rather than customized control strategies, while maintaining the same hardware. The PV is also utilized to provide reverse engineering analysis about the implemented control strategy for the ESC working in serial production mode.
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