The document compares using a clutch to provide damping instead of a dual mass flywheel in vehicle drivetrains. Testing showed the clutch controller reduced torsional oscillations during start up and gear changes by up to 39% and 69% respectively. It also decreased overshoot of clutch shaft speed by 25% and increased minimum engine and clutch shaft speeds. The controller successfully dampened oscillations and maintained vehicle speed and clutch demands. In conclusion, clutch micro-slipping showed potential to replace dual mass flywheels and provide cost savings.

1. Replacement of a Dual Mass Flywheel with a
Clutch in Micro-Slip
Project Scope
The aim of the project is to investigate the
use of clutch micro-slipping to provide
damping in vehicle drivetrains.
Results
The graphs below compare the dynamic response of the original model
output with the effect of clutch control.
•39% reduction in input torque overshoot after second gear is engaged
•69% reduction in input torque Peak-to-Peak oscillations during start up
•25% decrease of overshoot in clutch shaft speed
•83% increase of minimum clutch shaft speed whilst clutch disengages
•133% increase of minimum engine speed during transmission
The controller successfully reduces the torsional oscillations from the
system and is able to sustain the desired vehicle speed and clutch
demands.
DMF vs Clutch Control
• The Dual Mass Flywheel is a mechanical
device used to damp out torsional
oscillations in vehicle drivetrains.
•These oscillations degrade the quality of
gear changing and passenger comfort.
•In 1998 75% of gasoline vehicles and 67% of
diesel vehicles were fitted with DMFs (W.Reik et
al. ‘Dual Mass Flwheels’.
•Dual Mass Flywheels are expensive and add
weight to the system.
•It would be a major cost saving if the
damping could be performed by an existing
drivetrain component such as the clutch.
Conclusions
•Both linear and nonlinear models of the vehicle transmission system give realistic dynamic response representing torsional oscillations
during start up and gear change.
• Use of a single variable feedback system with both PID and Lag Compensators to control the clutch input force observing significant
reductions to the high frequency torsional oscillations in the engine drivetrain.
•In the modelling environment clutch micro-slipping is a successful contender to replace a Dual Mass Flywheel.
Method
First a linear model was built using Simulink modelling environment. The
‘Simulink Linear Model’ shows the complete system and the derived
equations that were used. This was done to analyse the system’s
resonance behaviour.
A more detailed model was developed using SimDriveline. This was
necessary to capture the strong nonlinear effects that are present during
low vehicle speeds. Furthermore components such as the clutch have a
complex friction coefficient which needs to be modelled accurately.
Inputs to the system model are clutch, throttle and gear signals. The
model outputs the speeds and torques along the vehicle driveshaft. The
clutch shaft speed is used as a feedback variable to control the clutch
signal in a limited region (micro-slip).
Leke Abolade, St Catherine’s College