Vehicle Automatic Seating Vehicle Automatic Seating SystemSystem

Computer Aided Design Computer Aided Design Fall 2004Fall 2004

Marian Rodríguez Marian Rodríguez Rebeca RiveraRebeca Rivera César César MoralesMorales

University of Puerto Rico University of Puerto Rico Mayaguez Campus Mayaguez Campus

Mechanical Engineering Department Mechanical Engineering Department

Video

Problem DescriptionProblem Description

Design a mechanism that Design a mechanism that will provide the mobility to will provide the mobility to the disable and aging people the disable and aging people to handle how to get in and to handle how to get in and out the car without that out the car without that much effort. much effort.

Expected OutcomesExpected Outcomes Provide a Provide a better quality of lifebetter quality of life for for

those who constantly need assistance those who constantly need assistance to sit and stand from a vehicle’s seat. to sit and stand from a vehicle’s seat.

Guarantee that the person sits and Guarantee that the person sits and stands from their seats in the stands from their seats in the safest safest possible waypossible way with or without help. with or without help.

The The person helpingperson helping will be also will be also beneficiatedbeneficiated because his or her because his or her function will only be to maintain the function will only be to maintain the person in the right direction towards person in the right direction towards or away the seat.or away the seat.

Design Selection-Idea #1Design Selection-Idea #1The seat of the car mounted on a lifting The seat of the car mounted on a lifting devicedevice

Lift the seat while outside the car Lift the seat while outside the car a maximum of 45°a maximum of 45°

A rotating mechanism A rotating mechanism A torque motor that will aid the A torque motor that will aid the

sliding movementsliding movement Sliding fixtureSliding fixture

Allow the seat to slide to the side Allow the seat to slide to the side out of the carout of the car

Provide the action of back and Provide the action of back and forth movement within the car forth movement within the car

A lifting device will lift the seat while A lifting device will lift the seat while outside the car a maximum of 45°. outside the car a maximum of 45°.

Design Selection-Idea# 2Design Selection-Idea# 2

The seat of the car mounted on a The seat of the car mounted on a lifting devicelifting device

Lift the seat while outside the Lift the seat while outside the car a maximum of 45°car a maximum of 45°

Sliding fixtureSliding fixtureS shape railings to aid for the S shape railings to aid for the back and forth movement along back and forth movement along with taking the car outside the with taking the car outside the carcar

A lifting device will lift the seat A lifting device will lift the seat while outside the car a maximum of while outside the car a maximum of 45°. 45°.

Design CriteriaDesign Criteria

CriteriaCriteriaWeightWeight Model 1Model 1 Model 2 Model 2

DatumDatum%% AutomatedAutomated ManualManual

CostCost 1515 -1-1 00 00ControlControl 2525 11 -1-1 00SpaceSpace 1313 00 -1-1 00User friendlyUser friendly 2020 11 -1-1 00MaintenanceMaintenance 88 00 00 00SafetySafety 77 11 00 00ManufacturingManufacturing 1212 00 00 00TotalTotal 100100 3737 -58-58 00

Design ProblemDesign Problem Analysis of the sliding mechanism is critical for Analysis of the sliding mechanism is critical for

safety and reliability. safety and reliability. The x-direction rails and guide blocks surfaces The x-direction rails and guide blocks surfaces

are in constant contact with each other suffering are in constant contact with each other suffering wearing, fatigue and bending.wearing, fatigue and bending.

Material Selection Material Selection

psiIMc 1435

Evaluation indexEvaluation index

Candidate MaterialsCandidate Materials

Ultra HighUltra HighStrength SteelStrength Steel

StainlessStainlessSteelSteel

LowLowCarbon SteelCarbon Steel

Ultimate Strength, psiUltimate Strength, psi 287,000287,000 206,000206,000 61,00061,000

Yield Strength, psiYield Strength, psi 270,000270,000 173,000173,000 51,00051,000

Young’s Modulus, psiYoung’s Modulus, psi 30x1030x1066 28x1028x1066 30x1030x1066

Hardness, BNHHardness, BNH 560560 -- 650650

Cost, US$/lb Cost, US$/lb 0.650.65 2.752.75 0.500.50

MachinabilityMachinability 5050 5050 6565

The stress in a The stress in a cantilever beam due to cantilever beam due to yielding:yielding:

Material Selected: AISI Material Selected: AISI 10201020

It is assumed that VASS will It is assumed that VASS will be used 10 times a day for 25 be used 10 times a day for 25 years. The cyclical stress at years. The cyclical stress at 101055 cycles of failure is cycles of failure is 38,000psi.38,000psi.

0

10

20

30

40

50

60

70

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08Cycles to failure, N

Stre

ss, k

si

OptimizationOptimization

where, where, EE is known as the Young’s Modulus of AISI 1020is known as the Young’s Modulus of AISI 1020PP is the applied load at two different pointsis the applied load at two different pointsaa is the distance from the fixed end to the first applied load is the distance from the fixed end to the first applied load PPbb is the distance from the fixed end to the second applied is the distance from the fixed end to the second applied load load PPll is the length of the cantilever beamis the length of the cantilever beamII is the moment of inertia of the beamis the moment of inertia of the beamδδ is the deflection at the end of the beamis the deflection at the end of the beam

ab

8.5 in

Part of theGuide Blocksinside the rails

lCantilever beam of length l

P P

EI

blPbalPaIPlba6

33),,,,(22

ConstraintsConstraints

05.81 abhEquality ConstraintsEquality Constraints

0617.12 Ih

01503 Ph

ab

8.5 in

Part of theGuide Blocksinside the rails

lCantilever beam of length l

P P

Inequality Inequality ConstraintsConstraints

05.13 and 012 21 lglg

025.3 and 075.1 43 agag

Finite Element MethodFinite Element Method

Results and DiscussionResults and DiscussionPresent DesignPresent Design xx*= {1.75 10.25 12 150 1.617}*= {1.75 10.25 12 150 1.617}TT

The deflection occurred at the free end as expected The deflection occurred at the free end as expected from a cantilever beam.from a cantilever beam.

The deflection is so small, δ = 0.0014 in, that The deflection is so small, δ = 0.0014 in, that guarantees that the guide block will not deflected.guarantees that the guide block will not deflected.

FEM Analysis shows that large blue areas are FEM Analysis shows that large blue areas are predominant; predominant; indicating an over design.indicating an over design.

In order to minimize the blue colors in the stress In order to minimize the blue colors in the stress gradient, modification to the cross-sectional area gradient, modification to the cross-sectional area could be performed.could be performed.

Cost AnalysisCost Analysis

$2,000, 16%

$4,000, 32%

$5,000, 40% $1,500, 12%

Investigation & Research Raw Materials Prototype Production

Conclusion and Conclusion and RecommendationsRecommendations

VASS offers:VASS offers:– A new perspective and opportunity for people A new perspective and opportunity for people

with disabilitieswith disabilities– A revolution and break all the standards A revolution and break all the standards

previously set by societypreviously set by society– A guarantee that for every individual the same A guarantee that for every individual the same

opportunities in social life will be availableopportunities in social life will be availableMechanical components needed to be Mechanical components needed to be

optimize:optimize: – The lifting mechanismThe lifting mechanism– The servomotor and torque motor The servomotor and torque motor – The Ball ScrewsThe Ball Screws

Final ThoughtFinal Thought

““The freedom that VASS The freedom that VASS provides is priceless. provides is priceless. There are lots of things to There are lots of things to see out there; so do not see out there; so do not limit yourself, the sky is limit yourself, the sky is the limit”the limit”

QuestionsQuestions

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