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Advances in Steering Mechanisms.(First step to steer by wire)

Presented by Arvind J. Bhosale

SMBS

OutlineOutline

1 Introduction

2 System Overview

3 Control Strategies

4 Literature Review

5 Applications and Benefits

6 References

7 Questions

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IntroductionIntroduction Mainly focusing on electro-mechanical power Mainly focusing on electro-mechanical power

steering steering

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IntroductionIntroduction

RequirementsShould be very accurate and easy to handleEffort required to steer should be minimumShould provide directional stabilityEasy alteration of driving direction

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IntroductionIntroduction

FunctionsTo achieve angular motion of the front wheels to

negotiate a turnTo provide directional stabilityTo provide perfect steering conditionTo facilitate straight ahead recovery after completing a

turnTo minimize tire wear

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IntroductionIntroductionClassification1.3.2 Based on the type of steering linkage or

mechanism used Ackerman steering mechanism Davis steering mechanism1.3.2 Based on the type of Front axle used For independent wheel suspension For rigid axles suspension1.3.3 Based on the Steering Gearbox used Rack and pinion type Recirculating ball type Worm and wheel type Cam and double roller type Worm and nut type

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IntroductionIntroduction

 1.3.4 Based on the type of power assist used Manual steering Power assisted steering• Hydraulic power steering

• Electro-hydraulic power steering

• Electric power steering

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System OverviewSystem Overview

Overview Of Electric Power SteeringNo requirement for hydraulic assistance (Eliminating

hydraulic oil )System provides assistance depending on the driving

conditionsSupports the “active return” functionEasier for the driver to steer the vehicle in a straight line

when the vehicle is being affected constantly by side winds or driven up or down hills

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System OverviewSystem OverviewTypes Of Electric Power Steering 1 Column type EPS

2 Pinion type EPS

3 Dual pinion type EPS

4 Offset Ball Screw type EPS

5 Direct drive type EPS

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System OverviewSystem OverviewThe electro-mechanical power steeringThe electro-mechanical power steering

with dual pinionwith dual pinion

System components Of EPS Steering wheelSteering column switch with steering angle sensorSteering columnSteering moment sensor(Torque sensor)Steering gearElectro-mechanical power steering motorPower steering control unit

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System OverviewSystem OverviewActual ViewActual View

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System OverviewSystem OverviewSchematic ViewSchematic View

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System OverviewSystem OverviewDisassembled viewDisassembled view

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FunctioningFunctioningThere are five general modes of operation of EPSThere are five general modes of operation of EPS

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FunctioningFunctioning

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FunctioningFunctioning

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FunctioningFunctioning

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FunctioningFunctioning

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Control Strategies Control Strategies

Control architecture consists of two layers of control

Effort level control (Torque Sensor) Assistance level control (Vehicle speed sensor)

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Control Strategies Control Strategies Effort Level Control Information like engine speed, and torque required are

transmitted to control module, which determines the optimal degree of assistance the electric motor should apply

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(Contd.)

Control StrategiesControl StrategiesEffort level control During any 120 degree interval of phase current I, the

instantaneous power (P ) being converted from electrical to mechanical is

P = ωT e = 2EI

T e = Electromagnetic torque

E = Induced EMF per phase.

E = 2NphBgLrω, per phase induced emf

Nph = Number of winding turns per phase

Bg = Rotor magnetic field density

L = Length of the rotor

r = Internal radius of rotor

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(Contd.)

Control StrategiesControl StrategiesEffort level control

Using the above expression the electromagnetic torque is given by,

T e = 4NphBgLrI = KφI

Where,

K = Torque constant

φ = Flux per pole pair

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Control Strategies Control Strategies Assistance Level Control Figure shows the effort required to be produced by the

motor for various vehicle speeds

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Literature ReviewLiterature Review

Historical background of Power steering

First power steering system was installed by a man with the surname of Fitts in 1876

Next power steering system was put on a Columbia 5-ton truck in 1903

First patent for power steering was issued to Robert E. Twyford (USA) on April 3, 1900

Francis W. Davis, in 1926 invented and demonstrated the first practical power steering system

The first commercially available passenger car power steering system introduced in the 1951 on the Chrysler Imperial

The first electric power steering system appeared on the Suzuki Cervo in 1988

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Literature ReviewLiterature ReviewControl map

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Literature ReviewLiterature Review

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Steering Effort

Literature ReviewLiterature ReviewComparison of energy consumption

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ApplicationsApplications

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BenefitsBenefitsNo hydraulic components, for example power steering

oil pump, hoses, oil tank, filterNo hydraulic fluidSpace savingsReduction in noiseEnergy savings(fuel saving by 4%)No complex hose and wiring systemGood straight-line stabilityDirect but soft application of the steering inputNo uncomfortable steering reactions over uneven

driving surfaces 

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ReferencesReferencesResearch Papers1 Srihari Vijayakumar and Ram Chandran., Analysis of an Electric Power Assisted

Steering System using Bond Graphs, SAE Paper No. 2003-01-05862 Shi Guobiao, Lin Yi., et al., Simulation of Straight-Line Type Assist

Characteristic of Electric Power-Assisted Steering, SAE Paper No. 2004-01-1107

3 A. Emre Cetin, Banu Sinanoglu., et al., Compliant Control of Electric Power Assisted Steering Systems, SAE Paper No. 2005-01-3535

4 R Murugan, S Nandakumar ., et al., DSP-based electric power assisted steering using BLDC motor Bharat Electronics Limited, Nandambakkam, Chennai

Books1 Lamm, Michael "75 years of Chryslers”  Popular Mechanics 176 (3): 75, Year

(March 1999)

Magazines1 Popular Mechanics, Hearst Magazines2 Power Steering: The Pioneer Unit, Popular Science 

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QuestionsQuestions

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