NUMERICAL SIMULATION TO IMPROVE ENGINE CONTROL … · NUMERICAL SIMULATION TO IMPROVE ENGINE...

NUMERICAL SIMULATION TO IMPROVE

ENGINE CONTROL

DURING TIP-IN MANOEUVRES

F. MILLO, C.V. FERRARO, F. MALLAMODIPARTIMENTO DI ENERGETICA

POLITECNICO DI TORINO

GT-Suite Users International ConferenceFrankfurt a.M., October 21st 2002

L. PILOFA-GM POWERTRAIN

Presentation overview

• Introduction

• Experimental set-up

• The engine model

• The vehicle and driveline model

• Model validation

• Evaluation of control strategies

• Conclusions

• Future work

Introduction

Vehicle driveability has nowadays undoubtedly become a key success factor for passenger cars, thus setting a further targetfor the designers besides pollutant emissions, fuel consumption and vehicle performance.

However, while the determination of fuel consumption and exhaust emissions follows well established standards, objective and reproducible criteria for the evaluation of a vehicle’s driveability are more difficult to be defined: a rating system based on the subjective assessments of experienced test drivers recorded during a sequence of relevant manoeuvres is usually employed.

One of the most common among these manouvres is the so called “tip-in”, that is a sudden opening of the throttle operated from conditions of low speed and low load.

Tip-in manoeuvres

Introduction

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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5time [s]

loa

d [

%]

Sudden opening of the throttleVehicle jerkings and acceleration fluctuations

The abrupt change of the torque delivered by the engine excites the torsional natural frequencies of the driveline, causing vehicle jerking and acceleration fluctuations, which are the main responsible for the driver’s and passengers’perception and assessment of perfomance and comfort.

Tip-in manoeuvres:The role of numerical simulation

Introduction

The vehicle’s behavior during tip-in is obviously determined by the powertrain design, but the engine management system may play a decisive role, especially with modern “torque based” systems, which are able to decouple the engine response from the driver’s demand by means, for example, of a “drive by wire” (DBW) throttle, that electronically filters the throttle valve opening command during fast acceleration transients, smoothing the vehicle response to sharpdriver’s requests.

However, since designing and tuning the engine control system still remains a time consuming activity, several efforts have been made to explore ways that could lead to significant reductions of thedevelopment process: in particular, the use of numerical simulation to build engine models by which control strategies can be tested and tuned “on a desk” seems to be very promising.

Tip-in manoeuvres:The role of numerical simulation

Introduction

The aim of this work is therefore to evaluate the potential of numerical simulation in the analysis of the dynamic transient response of a vehicle during tip-in manoeuvres, so as to reduce the experimental tests required to optimize the control strategies of the engine management system.


ü Introduction

• Experimental set-up





• Conclusions

• Future work

Experimental set-up

VEHICLE: FIAT PUNTO

MAIN ENGINE FEATURES

DOHC, 4 valves/cylinderDistribution

Multi-point electronic injectionFuel Metering System

107 Nm @ 4000 rpmMaximum Torque

52 kW @ 5000 rpmMaximum Power

Pent-roofCombustion Chamber

10.6 : 1Compression Ratio

1242 cm3Displacement

70.8 / 78.86 mmBore/Stroke

S.I. 4 cylinders in lineType

Experimental set-up

1 2 3 4

Alimentatore

Amplificatore Convertitore f-V

Analizzatore a/f

Amplificatore Convertitore f-V1. Giri ruota

2. Giri motore

3. Dosatura a/f

4. Apertura farfalla

5. Accelerazione longitudinale vettura

5

Segnali acquisiti

Elaborazione dati

Acquisizione dati digitale

Data analysisDigital acquisition

Amplifier

Amplifier

f-V Converter

f-V Converter

A/F AnalyzerPower supply

Acquired signals

1. Wheels angular speed

2. Engine angular speed

3. Air-Fuel ratio

4. Throttle opening

5. Vehicle longitudinalacceleration

DATA ACQUISITION SYSTEM


ü Introduction

üExperimental set-up





• Conclusions

• Future work

Main features of the engine model

The engine model

air inlet

air filter + Helmotz resonator

Close coupled catalyst

exhaust manifold

intake plenum + primary intake runners

connectingpipe + throttle

Validation of the engine model: full load conditionsGlobal quantities

The engine model

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240

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Bra

ke t

orq

ue

[Nm

]

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Bra

ke p

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kW]

SIM

EXP

The engine model

Validation of the engine model: full load conditionsInstantaneous quantities

-360 -270 -180 -90 0 90 180 270 3600

10

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40

50

60

Crank Ang le [de g ]

Pre

ssu

re

[b

ar]

experimentals imulation

W.O.T n = 4000 r.p.m.

Validation of the engine model: part load conditions

The engine model

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1

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8

9

10

0 200 400 600 800 1000inlet manifold pressure [mbar]

bm

ep [

bar

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EXPSIM

1500 rpm

ü Introduction


üThe engine model




• Conclusions

• Future work


• Front-wheel drive

The vehicle and driveline model

Schematic diagram of the driveline

Axle shaft

• 5 speed gear box

• Asymmetric axle shafts

9 DOF Torsional Model(Matlab-Simulink)

The vehicle and driveline model

1 2

3 4

7

5 6

8

9

C m o t C r e s

Equivalent inertia:1. Engine2. Clutch + Gear-box + Differential3. 5. Hub + rim4. 6. Tyres9. 9’. Vehicle

Engine torque

Load torque

9’

Load torque

9

865

743

21

Simulation Scheme

GT-Power Engine model

MATLAB -SIMULINK Driveline and Vehicle Model

Engine speed

Engine torque

Throttle

opening

A / F

ü Introduction


üThe engine model

üThe vehicle and driveline model



• Conclusions

• Future work


Example: 2nd gear - Initial engine speed: 1500 rpm

Model validation

Validation of the complete engine-vehicle model

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load

[%

]

Time history of the throttle opening

Engine angular speed: simulation vs experimental results

Model validation

Example: 2nd gear transmission ratio

Vehicle longitudinal acceleration: simulation vs experimental results

Model validation

Example: 2nd gear transmission ratio

ü Introduction


üThe engine model


üModel validation


• Conclusions

• Future work


Use of the model for the evaluation of control strategies

After the assessment of the accuracy and of the reliability of the complete engine-vehicle model, thenumerical simulation has been used as a prediction tool to analyze the impact of different control strategies on vehicle driveability during tip-in. The two following strategies were evaluated:

· drive by wire control

· spark advance control

Evaluation of control strategies

“Drive by wire” (DBW) throttle control


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load

[%

]

direct controlDBW

Time history of the throttle opening



Engine angular speed: comparison between DBW and direct control in 2nd gear



Vehicle acceleration: comparison between DBW and direct control in 2nd gear



Jerk and vehicle acceleration during tip-in:comparison between DBW and direct control in 2nd gear

Spark advance controller


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500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000n [rpm]

En

gin

e to

rqu

e [N

m]

basis advancebasis advance -6°basis advance -9°basis advance +3°basis advance +6°


Spark advance controller

Engine angular speed: comparison between simulation with and without spark advance controller


Spark advance controllerVehicle acceleration:

comparison between simulation with and without spark advance controller

ü Introduction


üThe engine model


üModel validation

üEvaluation of control strategies

• Conclusions

• Future work


A one-dimensional fluid-dynamic engine model was employed in conjunction with a Matlab-Simulink vehicle and driveline model to analyze the dynamic transient response of a gasoline passenger car during tip-in manoeuvres.

The numerical simulation was shown to be reliable and helpful for the study of proper control strategies of the engine management system aiming to enhance the vehicle driveability.

A detailed validation process of the complete engine-vehicle model, based on several sets of experimental data, wasperformed.

CONCLUSIONS

ü Introduction


üThe engine model


üModel validation

üEvaluation of control strategies

üConclusions

• Future work


Further investigations will be devoted to the improvement of the simulation of the vehicle acceleration, by means of more detailed models for the driveline and the vehicle.

FUTURE WORK

On the engine side the analysis will be extended to theevaluation of more detailed ECU models, in order to better represent the behavior of torque based systems.

Moreover, the use of more detailed combustion models to obtain essential information such as knock likelihood caused by sparktiming increases will also be evaluated.

FUTURE WORK

Example of a more detailed ECU model of a torque based system.

ACKNOWLEDGMENTS

The authors wish to thank:

• Gamma Technlogies for the support in the simulation activities;

• FA-GM Powertrain S.p.A. for the support and the permission to publish this work;

• Dr. Ferreri, Dr. Franchino and Dr. Tuttobene (Politecnico di Torino) for their helpful contribution during the experimental and simulation data processing.

A/F during tip-in

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