Limiting problematic Noise, Vibration and Harshness (NVH) phenomena in the modern automotive drivetrain is a task of critical importance. The result of such phenomena is the aggravation of the driver, which results in a reduced perception of vehicle quality. Each phenomenon can be characterized by a distinct frequency range. The aim of the current study is to assess the influence of the interfacial frictional behavior of the dry friction clutch components on the drivetrain dynamic behavior. The dynamics of the system (in terms of its stability) are studied. Surface data from the clutch components are critical to understanding the complex engagement process. The coefficient of friction was measured using a rotary tribometer at representative slip speeds and contact pressures. To aid the analysis infinite focus microscopy was used to measure the geometric properties of the constituent components of the drivetrain. The current approach allows for improved understanding of the drivetrain's dynamic behavior. The improved understanding of the coupling between tribological characteristics and drivetrain system dynamics can lead to the mitigation of future NVH issues.

Determining the root causes of various noise, vibration and harshness phenomena in modern automotive drivetrains is a critical task for industry, since noise, vibration and harshness issues often result in worsened driving experience. The aim of the current research is to investigate the dynamics during dry clutch engagement and the associated – often problematic – oscillations. This paper reports the development and partial validation of numerical models to study dry clutch behaviour. The models are used to investigate the influence of clutch and throttle actuation on the occurrence of unwanted clutch oscillations. The dynamic coefficient of friction between the clutch interacting surfaces was measured using a pin-on-disc rig under different slip speeds and contact pressure conditions, which are representative of a typical clutch engagement manoeuvre. The paper highlights the occurrence of instability issues in clutch dynamics (disc radial mode) as potential generators of aggressive noise, vibration and harshness, particularly during two different clutch pedal actuations. Such analysis has not hitherto been reported in the open literature.

<div class="section abstract"><div class="htmlview paragraph">Noise, vibration and harshness (NVH) phenomena can manifest themselves during the engagement and disengagement of dry friction clutch systems. Such phenomena can have a negative impact on cabin occupants’ driving experience as well as on others in the immediate vicinity of the vehicle. Typically, unwanted NVH phenomena that pertain to the clutch system include Judder, Chatter, Squeal and Eek. These are recognized by the quality of the radiated noise, as well as the dynamics occurring during clutch actuation. The aim of the current study is to utilize a numerical clutch system model (fully coupling the main motions of the clutch components) to predict clutch dynamics during engagement manoeuvres. The model will be used to assess the effect of various clutch design parameters on mitigating system instability. The clutch model utilizes measured coefficient of friction data from a rotary tribometer at representative slip speeds and friction surface contact pressures. The paper highlights potential NVH issues and demonstrates the improvement of such unwanted behavior through varying clutch system dynamic properties. Improved understanding of the parameters that affect clutch dynamic stability can lead to NVH improvement.</div></div>

Determining the root causes of Noise, Vibration and Harshness (NVH) phenomena in modern automotive drivetrains is a task of critical importance. This research investigates the stability of dry clutch systems vibrational behaviour during engagement. A fully coupled dry clutch numerical model including the influence of friction is presented and validated using vehicle measurements. The clutch component frictional properties are measured using parts that exhibit aggressive NVH behaviour using representative tribometric experiments. The validated numerical tool highlights the occurrence of instabilities which are caused by modal couplings, particularly between the input shaft bending and clutch disc radial motions. Such a validated transient dynamics model of a dry clutch system has not hitherto been presented in the open literature.

The automotive industry faces a continuous challenge to design vehicles that meet increasingly stringent regulations along with societal expectations. Often, any advancement towards meeting the prescribed design objectives may, without a fundamental understanding of the system-level behaviour, worsen the performance of the vehicle in another respect, creating Noise, Vibration and Harshness (NVH) issues. The development of physics-based transient dynamic models, of friction disc powertrain subcomponents (clutches and brakes), capable of predicting errant NVH behaviour is a highly desirable tool for the automotive industry to meet such contradictory design requirements.The aim of the current work is to investigate friction disc oscillatory response throughout the engagement process, link the frictional behaviour with the system dynamics and optimize the design parameters, using AI methods, for improving clutch NVH performance and oscillatory behaviour. A transient clutch dynamics model, which can accurately simulate typical engagement manoeuvres, is developed to identify potential unstable behaviour due to component unwanted motions. The coupling between torsional, tilting, bending and radial degrees of freedom, of the clutch components, is accomplished through the frictional interactions between component interfaces (clutch disc and pressure plate). The transient model is validated against experimentally obtained data from a vehicle and it utilizes coefficient of friction data, measured under representative interfacial conditions (pressure and relative speed) using a pin-on-disc machine. The model predicts clutch dynamic instability behaviour including: mode coupling instabilities along with the related system frequencies and mode shapes. A parametric study shows that the variation of geometrical parameters (pressure plate mass/clutch disc mass as well as the variation of system characteristics (stiffnesses and coefficient of friction) can lead to more than one mode coupling instability during the engagement process. The results from the parametric studies were used to develop a design optimisation process of the key system parameters (utilising a Recurrent Neural Network) for improving the NVH performance.