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

Advances in Steering Mechanism A.J.Bhosale

Outline1 Introduction2 System Overview3 Control Strategies 4 Literature Review5 Applications and Benefits6 References7 Questions

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Introduction Mainly focusing on electro-mechanical power steering

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

IntroductionFunctionsTo 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*

IntroductionClassification1.3.2 Based on the type of steering linkage or mechanism usedAckerman steering mechanismDavis 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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Introduction1.3.4 Based on the type of power assist usedManual steeringPower assisted steeringHydraulic power steeringElectro-hydraulic power steering Electric power steering

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System OverviewOverview 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*

System 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 OverviewThe electro-mechanical power steeringwith 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*

System OverviewActual View*

System OverviewSchematic View*

System OverviewDisassembled view

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FunctioningThere are five general modes of operation of EPS*

Functioning*

Functioning*

Functioning*

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Control Strategies Control architecture consists of two layers of controlEffort level control (Torque Sensor)Assistance level control (Vehicle speed sensor)

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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*(Contd.)

Control StrategiesEffort level control During any 120 degree interval of phase current I, the instantaneous power (P ) being converted from electrical to mechanical is P = T e = 2EI T e = Electromagnetic torque E = Induced EMF per phase. E = 2NphBgLr, 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*(Contd.)

Control StrategiesEffort level control Using the above expression the electromagnetic torque is given by, T e = 4NphBgLrI = KI Where, K = Torque constant = Flux per pole pair*

Control Strategies Assistance Level Control Figure shows the effort required to be produced by the motor for various vehicle speeds*

Literature Review

Historical background of Power steering

First power steering system was installed by a man with the surname of Fitts in 1876Next power steering system was put on a Columbia 5-ton truck in 1903First 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 systemThe first commercially available passenger car power steering system introduced in the 1951on the Chrysler ImperialThe first electric power steering system appeared on the Suzuki Cervo in 1988

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Literature ReviewControl map*

Literature Review* Steering Effort

Literature ReviewComparison of energy consumption*

Applications*

BenefitsNo 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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References

Research 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. 2004-01-11073 A. Emre Cetin, Banu Sinanoglu., et al., Compliant Control of Electric Power Assisted Steering Systems, SAE Paper No. 2005-01-35354 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 Mechanics176(3): 75, Year (March 1999)

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

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Questions*

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