Divesh Mittal

E- 579Mechatronics Modeling and Simulation

Term Project - “ Steer By Wire”

InstructorDr. Shuvra Das

Divesh Mittal

April 17, 2006 E-579 - Steer By Wire system 2

Contents

• Introduction• System level modeling

• Bond graph model

• SBW control

• Results and Discussion

• Limitations and Future work

• References


Introduction and Significance

• By wire system is getting popular because of its efficient and accurate operations.

• There are still few concerns and issues.• Idea here is to model simple steer by wire system and

see if we can replicate the results from existing hydraulic steering system.

• This is simple model to understand, idea needs to be extended in order to get more close to real world.


Problem Definition

• Understand and prepare system level model of Steer By Wire (SBW) system.

• Making the suitable assumptions to break down whole system into simple energy storage or dissipating elements.

• Convert above information into bond graph model and simulate it on 20-SimTM.

• Plot wheel angle and validate it with similar results from other references.


Steer By Wire System

[“Embedded Steer-by-Wire System Development”, Embedded World, 17-19 February 2004, Nuremberg, Germany]


Steer by Wire

Reference: http://www.Howstuffworks.com


• Introduction

• System level modeling• Bond graph model

• SBW control



• References


System Level Model

SBW

Steering Wheel Subsystem

Controller Subsystem

Front Wheel Subsystem

Steering Wheel Motor

Torque Sensor

Steering Angle Sensor

Steering Actuator (Motor)

Rack / Pinion Gear

Tire-Wheel subsystem

Steering Column

Tie rod

Control Unit

•Reactive torque

•Control Path


Modeling of SBW

• SBW system is composed of steering subsystem, controller and tire subsystem.

• Model subsystems with the help of major components.

• Each component is a combination of capacitive/inertia/resistor elements and is connected to other components with either a transformer / gyrator elements or series / parallel junction.


Block Diagram

Torque Input

Control Unit

DC Motor

Rack /pinion gear

Tire/wheel assembly


• Introduction

• System level modeling

• Bond graph model• SBW control



• References


Manual Rack and pinion steering system

ISteeringWheelInertia

RSteeringwheelresistance

0ZeroJunction1

CSteeringColumnStiffness

1OneJunction2

TFRackPinionGearratio

1OneJunction3

IMassofRack

0ZeroJunction2

1OneJunction4

CTieRodStiffness

RTieRodResistance

TFSteeringArmRatio

1OneJunction5

ITireInertia

MSeSelfAligningTorque Constant1

Integrate1

Constant4

Constant3

MSeMSe2

1OneJunction1

Steering wheel/ column Rack and pinion / tire

assembly


Without feedback/No control

1OneJunction1



0ZeroJunction1


1OneJunction2

TFRackPinionGearratio

1OneJunction3

IMassofRack

0ZeroJunction2

1OneJunction4

CTieRodStiffness

RTieRodResistance

TFSteeringArmRatio

1OneJunction5

ITireInertia

MSeSelfAligningTorque

MSeFrontWheelMotorVoltage

1OneJunction6

IArmatureInductance

RArmatureResistance

GYMotorConstant

1OneJunction7

IMotorShaftInertia

RMotorShaftResistance

0ZeroJunction3

CMotorShaftStiffness

TFGearMotorShaft

Constant1

Constant2

SeSe1

Front wheel actuator motor

Steering wheel

Rack/Pinion, tie rod and tire asembly


Data[3]


Front wheel angle

Front Wheel Angle ( Without Feedback)

0 1 2 3 4 5 6 7 8 9 10time {s}

-30

-20

-10

0

10

20

30

40

50

60

70

steeringwheelanglefrontwheelangle


Validation

Result from reference [1]


Front wheel angle Vs steering wheel angle

Front Wheel Angle vs Steering angle( Without Feedback)

0 5 10 15 20 25 30 35 40 45steeringwheelangle

-1

0

1

2

3

frontwheelangle

1.70

400


Steering subsystem

1OneJunction1



0ZeroJunction1


MSeSteeringwheelmotor

1OneJunction6

IArmatureInductance

RArmatureResistance

GYMotorConstant

1OneJunction7

IMotorShaftInertia


0ZeroJunction3

TFGearMotorShaft

Constant2

SeSe1

CMotorshaftcomplaince


• Introduction



• SBW control• Results and Discussion


• References


SBW Controller

• Steering wheel Motor Controller

• Front wheel actuator motor controller


Controller

SBW controller [3]


Steering Motor Controller

• Generates reactive torque.

• Easy to drive at low speed and vice versa.

• Reactive torque is function of velocity


Gain factor for Steering control

Gain for steering motor actuator [3]


Feed forward control

Bicycle model for steering behavior [3]


Steering Torque Controller

1OneJunction1



0ZeroJunction1


MSeSteeringwheelmotor

1OneJunction6

IArmatureInductance

RArmatureResistance

GYMotorConstant

1OneJunction7

IMotorShaftInertia


0ZeroJunction3

TFGearMotorShaft

Constant2

CMotorshaftcomplaince

drivertorqueinput

reactiontorque

velocity

drivertorqueMSeMSe2


Reaction Torque Control

Reaction Torque Control

0 1 2 3 4 5 6 7 8 9 10time {s}

-100

0

100

200

300

ExtratorqueVelocity {m/s}Driver Torque input {N.m}Reaction Torque


• Introduction



• SBW control

• Results and Discussion• Limitations and Future work

• References


Results

• Steer by wire was modeled using bond graph technology.

• Controller for SBW improves maneuverability and handling.

• Reactive torque can be controlled using torque control mechanism.


Proposed Time line VS Achievement Mapping

Proposed date Task Status

March 13 Topic search Achieved at time

March 20 Background research Achieved at time

March 27 Understanding the system Achieved at time

March 29 Proposal Presentation Achieved at time

April 02 Basic bond graph modeling Achieved at time

April 04 Decide on modeling complexity of sensors

Achieved at time

April 09 Modeling of controller Started at time but finished on April 15

April 11 Validation of results Achieved at time

April 17 Final presentation Achieved at time

April 21 Final report Should be done in time.


• Introduction



• SBW control


• Limitations and Future work• References


Limitations and Future Work

• Torque control mapping for steering motor.

• Front wheel motor voltage control.

• Importing Matlab file for lookup tables.


References

1. Srihari Vijaykumar ,”Analysis of an electric power assisted steering system using bond graphs”, SAE paper 2003-01-0586.

2. Srihari Vijaykumar ,” Application of bond graph technique to the design of passenger car steering system”, SAE paper 2002-01-0617.

3. Se-Wook Oh,” The development of an advanced control method for the steer-by-wire system to improve the vehicle maneuverability and stability”, SAE paper 2003-01-0578


Questions ??

Documents

Divesh Mittal