Hydraulic and Electrical Power Design Decision

Cynthia PerreiraCynthia PerreiraIMDL and SRLIMDL and SRL

Dr. Book and Dr. ParedisDr. Book and Dr. ParedisFebruary 21, 2003February 21, 2003

Introduction Two major power sources for mechanical devicesTwo major power sources for mechanical devices

Electrical Electrical HydraulicHydraulic

Decision not always made in best, most informed Decision not always made in best, most informed mannermanner

Decision is often made too early in the design Decision is often made too early in the design processprocess

Develop method of dealing with this type of Develop method of dealing with this type of decisiondecision

Introduction

Research into Electrical, Hydraulic power Research into Electrical, Hydraulic power as separate power sourcesas separate power sources

Little specifically comparing their Little specifically comparing their advantages/disadvantagesadvantages/disadvantages

Doesn’t appear to be any formalized Doesn’t appear to be any formalized method for making the choice between method for making the choice between themthem

Approach1.1. Develop a method for choosing between two familiesDevelop a method for choosing between two families

• Multiple Levels of choices/modelingMultiple Levels of choices/modeling• Performance MeasurementsPerformance Measurements• Develop systematic methodDevelop systematic method

2.2. Examine an example and apply the methodExamine an example and apply the method• Understand current technology choicesUnderstand current technology choices• Add to proposed methodAdd to proposed method• Apply proposed methodApply proposed method• Examine resultsExamine results

Power Tree Inside each family of power there are many Inside each family of power there are many

difference optionsdifference options

Composition

Selection

Electric Hydraulic Pneumatic

Drive System

OROR

linkagecylinder

ValvesActuator Pump

Rotational Translational Rotational Translational

OR OR

AND AND

AND

Multiple Levels of Modeling Selection between two Selection between two

families of solutionsfamilies of solutions Best family = family Best family = family

containing the best containing the best instanceinstance

Requires design Requires design knowledgeknowledge

Models at different levels Models at different levels of abstractionof abstraction

Hydraulic

Electrical

Performance

H

E

Levels of Modeling Simple modelsSimple models

F=maF=ma P=TvP=Tv

Rules of thumbRules of thumb Known values for groups of componentsKnown values for groups of components SimulationSimulation

MatlabMatlab ModelicaModelica

Performance Measurements Power outputPower output Velocity, TorqueVelocity, Torque Geometry, space requiredGeometry, space required WeightWeight EfficiencyEfficiency CostCost NoiseNoise Other application specific factorsOther application specific factors

Applications of Fluid Power AutomotiveAutomotive

DriveDrive BrakesBrakes Power SteeringPower Steering

Manufacturing machineryManufacturing machinery Construction equipmentConstruction equipment

LoadersLoaders CranesCranes BulldozersBulldozers

RobotsRobots ElevatorsElevators

Power Steering Example Technology that lends Technology that lends

itself well to the use itself well to the use of either hydraulic or of either hydraulic or electrical powerelectrical power

Currently dominated Currently dominated by hydraulicsby hydraulics

Electro-hydraulic Electro-hydraulic systemssystems

Electrical recently Electrical recently implemented in some implemented in some new small carsnew small cars

***Contacts with NSK, Ford, Siemens

Hydraulic Power Steering

Electro-hydraulic Systems

Electric motor to power steering pumpElectric motor to power steering pump Speed of motor can be varied or turned offSpeed of motor can be varied or turned off Can be used for large and small vehiclesCan be used for large and small vehicles AdvantagesAdvantages

Better fuel efficiencyBetter fuel efficiency Motor can turn off when not in useMotor can turn off when not in use Less energy consumptionLess energy consumption

Electrical Power Steering

Electrical Power Steering AdvantagesAdvantages

EnvironmentEnvironment Off when not turningOff when not turning Lower weight and sizeLower weight and size Energy consumption as little as 1/20 of hydraulicEnergy consumption as little as 1/20 of hydraulic Can reduce fuel consumption by 3-5%Can reduce fuel consumption by 3-5% Contains no oilContains no oil

Better feel when drivingBetter feel when driving Reduced rattling noiseReduced rattling noise

DisadvantagesDisadvantages CostCost Low force output – only currently suitable for small carsLow force output – only currently suitable for small cars

42V may allow the system to be used in heavier vehicles with larger tire contact 42V may allow the system to be used in heavier vehicles with larger tire contact patches patches

Now present in 2002 Saturn Vue, Honda Civic SI, Honda InsightNow present in 2002 Saturn Vue, Honda Civic SI, Honda Insight

Future Work

Further develop systematic methodFurther develop systematic method Determine levels of modeling and Determine levels of modeling and

information needed at eachinformation needed at each Relate measures of performance to Relate measures of performance to

customer’s wishescustomer’s wishes Continue with power steering exampleContinue with power steering example Continue contacts with Ford, NSKContinue contacts with Ford, NSK

Questions?