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Dynamics and Vibrations of Mechanical Systems

Relatori: Prof. Edoardo Sabbioni, Prof. Federico Cheli

Tutor: Prof. Massimiliano Gobbi

Università di Provenienza: Politecnico di Milano - Ingegneria Meccanica

Titolo della Tesi: Modeling and experimental tests of a vehicle driveline aimed at identifying key parameters affecting idle rattle

Modeling and experimental tests of a vehicle driveline aimed at identifying key parameters affecting idle rattle

Introduction

To analyse the rattle phenomena two main tools have been developed:

  • MB (Multibody Model) model have beendeveloped to study idle rattle noise comingfrom the engine side.
  • 1D torsional dynamic model have beendeveloped to focus on idle rattle and gearrattle noise coming from the gearbox side.

Objectives

  • The aim of the research activity is to develop a series ofdynamics models (Multibody and 1D torsional dynamic) toidentify key parameters affecting driveline rattle.
  • With the developed tools, the car manufacturer wants toanalyse phenomena like idle rattle and gear rattle during thedesign phase of the car.
  • The results of the model’s simulations must guide the researchto propose hardware and software solutions to the rattlephenomena present on the studied vehicle.

Results

Concerning Idle Rattle (Fig. 3, Fig. 4, Fig. 5, Fig. 6):

  • It has been experimentally proventhat large radial movements oftransmission bell-shaft are related tospikes acquired by the accelerometeron engine bell-housing.
  • The accelerometer spikes are alsoassociated with spikes acquired bythe microphone on the driver seatand also with the driver perception.
  • MB simulation model is capable toreproduce bell-shaft dynamics.
  • A solution for idle rattle has beenproposed based on new bearingslayout and reduced unbalance of theflywheel.

Concerning Gear Rattle (Fig. 7, Fig. 8):

  • It has been experimentally proven that largeangular torsional vibration on DCT (Dual ClutchTransmission) are associated with high valuesof vertical acceleration on the gearbox andwith driver perception.
  • A metric to quantify gear rattle magnitude(MGR) has been developed based on theacquired vertical acceleration on the gearbox.
  • 1D simulation model is capable to replicatetorsional vibration at DCT.
  • A software strategy based on clutch slip controlhas been developed to reduce torsionalvibration, reducing therefore gear rattle.

Conclusions

Main Conclusions & Considerations:

  • The research activity has been focused on the development of simulation tools tounderstand rattle phenomena, such as idle rattle and gear rattle.
  • The MB simulation results showed the path for a powertrain hardware change tomitigate idle rattle issue. The proposed solution reached the production line of the car.
  • The 1D torsional model showed evidence of relationship between the complained gearrattle and high torsional vibration at DCT level. A software strategy solution has beenproposed based on simulation results and is today implemented in production cars.
  • This research involved several innovations, such as the 3D MB model of the Dual MassFlywheel and the Clutch Slip Control strategy.

References

G. Quattromani, A. Palermo, F. Pulvirenti, E. Sabbioni, F. Cheli, Nonlinear 3D Dynamic Model of an Automotive Dual Mass Flywheel, in Rotating Machinery, Hybrid Test Methods, Vibro-Acoustics & Laser Vibrometry, 2017.
G. Quattromani, Powertrain multibody modelling of front engine - RWD: Analysis of idle dynamic and NVH, in EAWD, Graz, 2019.