NVH vs. Vehicle Fuel Economy Trade-off

Mario Felice, Jack Liu, Imad Khan Ford Motor Company

Jonathan Zeman, Llorenc Gomez Gamma Technologies

Wulong Sun MSC Software

Michael Platten Romax Technology

2015 North American GT Conference, Nov. 9th

Introduction • Study of the fuel economy vs. NVH (Noise Vibration and Harshness) trade-off of

a 4 cylinder AWD vehicle with a 6 speed automatic transmission integrating technology from 3 partner software suppliers – Gamma Technologies for Engine and Torsional Damper – MSC Adams for 3D Driveline and Chassis – RomaxDESIGNER for Transmission and PTU (Power Take-off Unit)

• Four main aims: – Predictively quantify fuel economy penalty for slipping TCC (Torque

Convertor Clutch) – Predictively quantify transmission torsional vibration and seat track

acceleration amplitudes for locked and slipping TCC – Predictively quantify drivetrain lugging and rattle NVH responses under

damper designs and slipping TCC – Evaluate other damper technologies as an alternative to TCC slip – Understand details and benefits of software co-simulation and model

reduction

Software Usage Overview

Adams full vehicle and driveline mode

Engine Behavior

Predictive GT-POWER engine gives physically accurate engine torque and fuel consumption output as a function of engine rpm and load request

GT-Suite Damper Models • Models of three common used damping technologies to

reduce the oscillatory characteristic of the engine torque – Conventional Damper

• Controlled slip from 0-60RPM in 10RPM increments – Series Double Damper – Centrifugal Pendulum Absorber (CPA)

• Modeled with 1D+2D planar components

Conventional Damper

Series Double Damper

Pendulum Absorber

GT-Suite Damper Models • Steady-state damper isolation performance curves

6F35 with PTU in RomaxDESIGNER

Dynamic FUSION discretizes and exports a time-domain 1D/3D MBD model

Visualization of Adams format of Romax model

Dynamic FUSION Workflow Dynamic FUSION can export a native 3D Adams file, or generic XML file, which can be read by GT-SUITE to create a 1D torsional-only model

Model Setup and Co-simulation • Merged chassis, transmission and driveline models

• Dynamic engine speed sweep from 800-3000 RPM at full load with Rear Differential Unit (RDU) clutch locked

• GT-SUITE co-simulates with Adams, exchange transmission input shaft speed and torque data

Adams Vehicle Model Romax Trans/PTU Model

Adams Drivetrain Model

GT Engine Model Romax/Adams Model

Co-simulation

• Transmission Output Shaft RMS Speed Amplitudes – Conventional Damper with Slip

Co-Simulation Results: TCC Slip

Driveline resonance

Co-Simulation Results: Damper Types

Driveline resonance

Co-Simulation Results: Resonance at damper mode

Baseline Lugging Limit

CPA Lugging Limit

Co-Simulation Results: Seat Track Vibration

Seat Track Acceleration: TCC Slip with Conventional Damper

Seat Track Acceleration: Damper Design

Co-Simulation Results: Seat Track Vibration 2nd Order Cut

Seat Track Acceleration: Damper Design

*Shift of 2nd order response due to torque converter slip is due to increasing engine starting speed with increased amounts of slip

Seat Track Acceleration: TCC Slip with Conventional Damper

— 0RPM Slip ― 20RPM Slip — 40RPM Slip — 60RPM Slip

Baseline (0 TC slip)

Co-Simulation Results: PTU Rattle

RDU Open (7Nm constant drag) Gear Lash in Driveshaft: 2 Degree Full Throttle, 5th gear position Various TCC Slip (0 – 60 rpm)

Vehicle Model Setup Model Outputs PTU rattle torque Drivetrain torsional vibration Drivetrain torsional modes Seat track vibration

Relative Gear Displacement Torque on Gear

Rattle Rattle Rattle Rattle

Driveshaft Torsional Mode at Rattle ~59Hz

Co-Simulation Results: PTU Rattle Baseline (0 TCC slip) Linear Mode Animation

59 Hz

Frequency domain

Time domain + FFT Rattle

Rattle Peak

TCC Slip reduces PTU rattle response Relative Gear Displacement

Torque on Gear

Co-Simulation Results: PTU Rattle

0 rpm 30 rpm 60 rpm

0 rpm 30 rpm 60 rpm

Co-Simulation Results: PTU Rattle Comparison of damper design vs. TCC slip

Relative Gear Displacement

Torque on Gear

0 rpm 40 rpm Double CPA

0 rpm 40 rpm Double CPA

Co-Simulation Results: Fuel Economy • TCC slip has negative impact on fuel economy

– Damper design has negligible effect on fuel economy

Conclusions • This paper performs the FE evaluation based on special

driving maneuvers – Lugging results show a high fuel economy penalty for TCC slip – However, a complete certification driving cycle will not exhibit the

same penalty • Compare baseline TCC slip map (40 rpm max) with a more

aggressive lockup map, which could be realized with a different damper

FTP75 HFET US06 NEDC

Modified Slip Map 1.5% 0.22% 1.4% 0.30%

Fuel Economy Penalty vs. Driving Cycle

Conclusions

• This paper demonstrates a powerful method in evaluating predictive tradeoff of fuel economy and NVH – An optimal design best balancing fuel economy and NVH can be

analytically determined before prototypes are built

• This method is also applicable for predicting tradeoff of cost

vs. performance, and fuel economy