Generic EPS DVP and Robustness

Plan

Costas Chrysochoidis

1

CONTENTS

O REDPEPR

O Reliability Growth Plan

2

OBJECTIVE

LAUNCH

A

VALIDATED

&

ROBUST

PRODUCT

3

VALIDATION REQUIREMENTS

O Specified in OEM subsystem specification:

Tier 1 supplier:

O Vehicle End of travel test

O Steering Gear End of travel test

O EPS Unit tests

O Steering Gear tests (gear, ITR,OTR, Bellows)

O Other validatable requirements

OEM:

O Vehicle tests (Durability, Thermal, NVH, Water Intrusion)

O Lab tests (gear to cradle/frame durability, 445 N strg rim pull)

4

Robustness Performance Monitoring thru

CV/DV/PV

O Monitor Reliability growth in terms of: O Global and O LOA, NVH, Sealing, other

O Monitor with metrics performance relative to the

decided High Impact Error States: O Friction O Noise (running, rattle, clunk, buzz) O Excessive SRS O Lack or Loss of assist O Poor on center precision O Water Ingress O Mechanical Failure

5

REDPEPR Program: GM Epsilon

Author: Costas Chrysochoidis_5MAR10

System/Function: BD REPS VERIFICATION METHODS

IDEAL FUNCTIONS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

HIG

H I

MP

AC

T

ER

RO

R S

TA

TE

S

VM TYPE

K K K

X J Mechanical Failure J J X X X X X X X X X X X X X X

X I water ingress I I X X X X X X X X

X H Transfers poor on center precision to driver H H X X X X X X X X X X X X X

X G Lack or Loss of Assist G Cat Strategy G X X X X X X X X X X X X X X X X

X F Excessive SRS F I Change Technology F X X X X

X E NVH - IPA Buzz noise E II Apply Parameter Design E X X X

X D NVH - reversal noise D III Upgrade Design Spec. D X X X X

X C NVH - rattle noise C IV Reduce / Remove Noise C X X X X

X B NVH - Running noise/zipper noise (tonality) B V Add Compensation Device B X X X X X X

X A Friction A VI Disguise / Divert A X X X X X X X X X X X

VII Other HIGH

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X IMPACT

A B C D E F G H I J K L M N O NFMS Descriptions

NOISE 1: Piece to Piece Variation NF1

a) a) X X X X X X X

b) b) X X

c) c) X X X X X X X X X X X X X X

d) d) X X X X X X

e) e) X X X X X X X X

f) f) X X

g) g) X X

h) h)

I) I) X X X X X X X X X X X

j) j) X X X X X X X X X X X X

k) k) X X X X

l) l) X X X X X X X

m) m) X

n) n) X X X X X X X X X X X X X X X X

o) o) X

p) p) X X X X X X X X X X X X

q) q) X

r) r) X X X

s) s) X X X X X X X

t) t) X X X X X X X X X X X X

u) u) X X X X X X X X X

v) v) X X X X X X X X X X X X X

w) w) X X X X

x) x) X X X X X X X X X X

y) y) X X X

z) z) X X X X X X X X X

aa) aa) X X X

ab) ab) X X

ac) ac) X

ad) ad) X X

ae) ae) X X

af) af) X X

NOISE 2: Change Over Time NF2

a) a) X X X X X X

b) b) X X X X X X X X X

c) c) X X X X X

d) d) X X X X X X X X X X X

e) e) X X X X X X

f) f) X X X X X

g) g) X X X X X X

h) h) X X X X X

I) I) X X X X X

j) j) X X X

k) k) X X X X X

l) l) X X X X X X

m) m) X

n) n) X X X X X

NOISE 3: Customer Usage NF3

a) a) X X X X X X X X X X X X X

b) b) X X X X

c) c) X X

d) d)

e) e) X X X X X

f) f) X X X X

g) g) X X X X X X X X

h) h) X X X X X X X X X X X X

I) I) X X X X X X

j) j)

k) k)

l) l) X X X

m) m) X X X

n) n) X X X

o) o) X X X X

p) p) X X X X X X

q) q) X X

r) r) X X

s) s) X X X X X X

t) t) X X X X X X

u) II u) X X X X X X X X

v) v) X X X X X X X X

NOISE 4: External Environment NF4

a) a)

b) b) X X X X X X X

c) c) X X X X X X X X X

d) d) X X X

e) e) X X X X X X X X X X X

f) f) X X X X X X X X X X X

g) g)

h) h) X X X X

I) I) X X X X X X X X X X X X

j) j) X X X X X X X

NOISE 5: System Interaction NF5

a) a) X X X

b) b) X X X X X

c) c) X X X X X X X X X

d) d) X

e) e) X X X X

f) f) X

g) g) X X X X X X X

h) h) X X X X

I) I) X X X

j) j) X X

k) k)

l) l) X

m) m) X X X X

n) n)

o) o) X X X X

p) p)

q) q) X X X X X X X X X

CONTROL FACTORS NF1

a) a) X X X X X

b) b) X X

c) c) X X X X X X X X

d) d) X X X X X

e) e) X X X X X X

f) f) X X X X X X X X X X X X X X X X

g) g) X X X X X

h) h) X X X X X X X X X

I) I) X X X X X X

j) j) X X X X X X X X X

k) k) X X X X X X X X

l) l) X X X X X X X X X X X X X X X

m) m) X X X X X

n) n) X X X X X

o) o) X X X X X X X X X

p) p) X X X X X X

q) q) X X X X

r) r) X X X X X X X X X X X

s) s) X X X X X X X X X X X

t) t)

u) u) X X

v) v)

w) w) X

x) x) X X X

y) y) X

z) z) X X X X

aa) aa) X X

ab) ab) X X

ac) ac) X X

ad) ad) X X

ae) ae) X X X X

af) af) X

ag) ag) X

ah) IV ah) X X

ai) ai) X X

aj) aj) X X X

ak) ak) X X X

SEALING CONTROL FACTORS NF2

a) III a) X

b) III b) X

c) III c) X

d) III d) X

e) III e) X

f) f) X

g) III g) X

h) III h) X

I) III I) X

j) III j) X

k) k) X

l) l) X

m) m) X

n) n) X

o) o) X

EPP to pinion housing

Threaded yoke cover to pinion housing ISO fit

Yoke plug (rubber) to yoke cover (as cast hole) mmmax yoke ID

(min fill)max yoke ID (min fill)

Seals between female and male connectors (TRW TS, GM power and comm)

ECU lid to motor casting and plastic connector header to motor casting mm

Radial clamp over Santoprene bellow to inner tie rod mm

ITR groove

min OD/max

width (min fill)

ITR groove min OD/max width (min fill)

Oetiker clamp over Santoprene bellow to pinion housing mm, N

min hsg OD,

max groove,

min clamp

min hsg OD, min bellow thickness,

max groove, min clamp force (min

fill)

harness to pinion housing mmmax PH ID

(min fill)max PH ID (min fill)

Input shaft to torque sensor cover mm

min IS OD-

max TSC

ID/height

min IS OD-max TSC ID/height (min fill)

Pinion plug threaded interface to pinion housing ISO fit

o-ring-Pinion plug to pinion housing mm

plug min

OD&max

height/max

plug min OD&max height/max hsg OD (min fill)

o-ring groove width-Torque sensor cover to pinion housing mm max (min fill) max (min fill)

o-ring groove depth-Torque sensor cover to pinion housing mm max (min fill) max (min fill)

face seal groove width-Pinion to Outboard Housing Face Seal mm max (min fill) max (min fill)

face seal groove depth-Pinion to Outboard Housing Face Seal mm

max (min fill)

and min

(stability)

max (min fill) and min (stability)

bias to be used for the mule build based

on Eng'g judgement

OBJ lash

IBJ lash

Yoke o-rings compression

t-bar bearing design (bearing vs.bushing)

Yoke radial clearance mm 0.008 - 0.052

Yoke axial clearance mm 0.050 - 0.110

Yoke spring rate/ mesh load setting - spring force N 340 +/-10%

4-pt bearing surface finish Ra microns tbd

RBNA nut surface finish Ra microns tbd

RBNA rack race waviness tbd tbd

RBNA rack race surface finish Ra microns 0.4

Gear set tolerance - Rack/Pinion mesh tbd tbd

4-point bearing lash microns 10 - 25

RBNA lash microns 15 - 21

Alignment of pinion housing to TSC (concentricity)

4-point clearance between bearing OD and hsg ID

T-bar rate Nm.deg 2.5 +/-

Rack Travel tolerance

Flatness tolerance of gear mounting

Position tolerance of gear mounting

Housings porosity

Soft stop stiffness

Fastener Torques (inner & outer spanner nut, hsg bolts, harness, connector, ITR to rack)

clamp loads

ITR Buckle strength

Gear mounting bushes

Control algorithms

Housings strength

Belt design (including mass? )

Rack strength

Pinion strength

Lubrication properties

Rack Liner to rack clearance

rack liner wear properties

Motor design

Gear reduction ratio (column to motor ratio) ratio GMX: 22.4 / XTS 24

Torque sensor accuracy / precision / resolution /redundancy

Tires and Wheels (Modes and mini spare) tread, Hz

Non uniformity TBD

Alignment input shaft to steering column mm

AC Evaporator drip / cowl drainage (Water) gr/min

EMC interference / ESD V/microsec

CAN signal availability and quality logic, tbd

CAN connector and harness resistance mohms

Upper steering loads, stiffness, friction, and modes Nm, Hz

Powertrain modes Hz

Heat (powertrain exhaust) deg C

Subframe flatness of gear mounts mm

Voltage spikes V/micro sec

Power supply voltage (Battery) V

Power Connector and harness resistance mohms

Suspension loads, friction modes N

Subframe structure loads and modes kN, Hz

Body structure modes Hz

Driving on extremely crowned road type

Road surface type

EMC interference / ESD V/micro sec

Agressive industry polution (Ozone / SOx, etc.) mgr/cc

Water/Humidity (as noises only relevant after failed sealing or cut boot) outside design windowgr, RH TBD, 5 - 100%

Dust and Dirt (as noises only relevant after failed sealing or cut boot) outside design windowtype, mgr/cc

Mud/Slurry (as noises only relevant after failed sealing or cut boot) outside design windowtype, mgr/cc

Saltwater (as noises only relevant after failed sealing or cut boot) outside design windowtype, mgr/cc

Ambient Temperature outside the vehicle deg C -40 to 130

Vehicle Shipment - Shock exposure logic

Loose BNA ball logic true/false

Cut boot logic true/false

Damaged PH datum (handling) logic true/false

Broken PH (IPA tower) logic true/false

TS bent finger logic true/false

TS wire harness damage logic true/false

Vehicle Load incl. Trailer (weight) kN spectrum

Engine idling for a long time in very hot environment hrs, degC 1 hr?, 130 degC

Low mu end lock impact (power on) motor rev/min~2000

Workshop Misuse motor rev/min~2000

Car wash cleaning agents and spray list SSTS

Reverse polarity V

Jump starting vehicle with non 12V system V

Submerged driving water temp deg C0 - 5

Extreme off road driving kN spectrum

Vehicle loads (max load) kN spectrum

High Loads impacts kN 20+

Tire/Wheel Change tread sizes

Improper service interval (bellows/tie rods)

Customer fluids/chemical compatibility list SSTS

Extreme handwheel torque (while power off) Nm

Temperature range deg C -40 to 125

4-pt bearing lash increase over time mm

Compression set or plastic creep of rubber seals %

Outer Spanner nut pre-torque decay Nm

Inner Spanner nut pre-torque decay Nm

Leak rate (correlation to water leak paths following operation cycles) ccm

RBNA efficiency decay %

EPP efficiency decay %

Ball nut lash increase mm

Sealing degradation (->Corrosion) ccm

Yoke clearance increase mm

Belt tension decay Hz

Lubrication property changes

Friction decay IS Nm

Pinion Nut torque Decay Nm

TSC bearing to IS clearance mm 0.040 - 0.072

belt teeth misalignment (axial offset & fleeting angle-pulleys assy related) mm & deg CARS 10-00364

Misalignment of RBNA nut races to rack races mm & deg CARS 10-00364

Boot stiffness N/mm 1.05 - 1.10

IS Seal friction (RSS) mNm

Strength of Assist reduction mechanism (belt/pulleys) Nm

Efficiency of Assist reduction mechanism (belt/pulleys) %

Compliance of Assist reduction mechanism (belt/pulleys) deg/Nm

Friction of Assist reduction mechanism (belt/pulleys) Large Pulley Nm

BNA friction p-p @ x mm/s N

RBNA mean friction @ x mm/s N

Large pulley runout in assy Hz deg +/-25 +/-4

Small pulley runout in assy Hz deg +/-50 +/-2

Belt mass gr

EPP torque ripple (9th order) mNm

EPP friction p-p (cogging) @x rpm, power on currently not measured

EPP mean friction @x rpm, power on mNm

EPP cogging (friction p-p) @x rpm power off mNm

EPP mean friction @x rpm power off mNm

System natural frequency (modal alignment) Hz >>34

Transmission error mm/rev 0 - 0.30

Motor Inertia 10 -̂4 kg.m 2̂69:2.25/78:2.54 +/- 5%

TS functionality (ASIC jitter, short, solder Joint) logic true/false

EPP functionality logic true/false

IPA natural frequency (IS to Pinion gap, other gaps/lashes) Hz

Kinematic Hysteresis deg 0 - 0.5

BNA noise m/s 2̂

RBNA efficiency %

Leak rate (correlation to water leak paths) cc/min tbd

Belt tension N 80 - 100

EPP housing vibration (9th order) m/sec 2̂ tbd

STRATEGY (NFMS)

Metric Range

EPP efficiency %

10 years of environmental exposure and 160900 km of extreme customer usage (99.9 percetile)

ERROR STATES

NOISE FACTOR MANAGMT

Power assist

On center precision (Vehicle Dynamics Attribute)

GM

Veh

Dyn

am

ics

TR

W V

eh

Ratt

le N

ois

e t

est

Revers

al

No

ise t

est

Bu

zz n

ois

e t

est

GM

Veh

Th

erm

al

GM

Veh

NV

H

GM

Veh

wate

r in

tru

sio

n

GM

Veh

En

d o

f tr

avel

Cu

t B

oo

t

GM

ste

eri

ng

to

cra

dd

le

GM

100 l

bs r

im p

ull

GM

Veh

Du

rab

ilit

y

Imp

act

En

d o

f T

ravel

Test

Vacu

um

/Pre

ssu

re a

ir l

eak t

est

BU

LL

Y

Vib

rati

on

Gear

En

vir

on

men

tal

Wear

an

d W

ate

r S

ub

mers

ion

Co

rro

sio

n

Tem

p S

ho

ck W

ate

r S

ub

mers

ion

/hig

h p

ressu

re S

pra

y

EP

S U

nit

Wear

Test

Gear

Wear

an

d F

ati

gu

e (

Du

rab

ilit

y)

Gear

Hig

h L

oad

Fati

gu

e

Gear

Wear

(po

wer

on

)

EP

S U

nit

Lash

Ch

em

ical

Exp

osu

re -

Un

derh

oo

d

Du

st

Han

dw

heel

To

rqu

e

Co

ld S

tart

Eff

ort

s

Du

ty C

ycle

Cap

ab

ilit

y/P

ark

ing

du

rati

on

Max P

oth

ole

(kic

k b

ack)

Ste

eri

ng

Eff

ort

- P

ow

er

Assis

t O

ff (

EE

C92/6

2)

Sta

tic E

ffo

rt V

ari

ati

on

wit

h T

em

p a

nd

Vo

ltag

e

Dyn

am

ic E

ffo

rt V

ari

ati

on

wit

h T

em

p a

nd

Vo

ltag

e

Co

ld S

tart

No

ise

Ho

t T

em

pera

ture

No

ise

Axia

l/R

ad

ial

Ste

eri

ng

Gear

Inp

ut

Sh

aft

Co

mp

lian

ce

Dete

rmin

ati

on

of

C-F

acto

r

Ela

sti

cit

y/B

ackla

sh

rack t

o p

inio

n

Inert

ia C

om

pen

sati

on

Ste

eri

ng

No

ise A

llo

wan

ce

SC

F

SR

S

Kin

em

ati

c H

yste

resis

Po

wer

On

Displacement (mm) of tie rods/rack bar

Force (N) on tie rods/rack bar

Ste

eri

ng

Eff

ort

Ch

an

ge w

ith

Han

dw

heel

Sp

eed

Ste

eri

ng

To

rqu

e P

ow

er

On

/Off

R+

P I

nte

rface C

om

pli

an

ce (

yo

ke c

leara

nce)

Retu

rnab

ilit

y P

ow

er

On

On

-Cen

ter

Retu

rnab

ilit

y P

ow

er

On

Retu

rnab

ilit

y P

ow

er

Off

Bo

ost

Ch

ara

cte

risti

csUSEFUL LIFE PERIOD

B - Bogey

D - Degradation

F - Failure

VM Types

Strong =

Weak =

None = Blank

Interaction

6

Parameter Design Applications …

A. FRICTION

Ensure NF/CF traceability to run capability and correlations

Measure tension at 4 positions

Record belt mass

B. RUNNING NOISE

DOE: 8 run 1/16 fractional Factorial – seven factors

C. RATTLE NOISE

DOE: 8 run full Factorial – three factors

D. CLUNK NOISE

DOE: 8 run full Factorial – three factors

E. BUZZ NOISE

Test max TSC bearing to IS clearance with nominal (centered) IPA and

Pinion Housing

7

Parameter Design Applications continued

F. SRS

DOE: 16 run 1/256 fractional Factorial – twelve factors

Simulation model: characterize gear components for damping/spring properties and solve for required properties

G. LOA

Evaluate with repetitive ignition cycling and other CV testing

H. OCP

Define the target dynamic S plot (Input torque vs. rack load)

DOE: 8 run 1/16 fractional Factorial – seven factors

I. WATER INGRESS

Define program specific leak testing and investigate correlation to water leak paths

Evaluate the most likely worst case condition for the sealing joints

J. MECHANICAL FAILURE

Evaluate with OEM Validation Testing

Apply Overstress Probing (four candidate tests) 8

CV Robustness Samples

ITEM # QTY PART REQUIREMENT USAGE

1 3 IPA MAX transmission error (MAX CRE) 1 CLUNK, 1 SRS, 1 OCP

2 3 IPA MIN transmission error (MIN CRE) 1 CLUNK, 1 SRS, 1 OCP

3 1 IPA ALL DIMS NOMINAL (ZERO runout) w /min IS OD (same as in sealing) BUZZ

4 2 IPA 1.5 Nm/deg MAX transmission error (MAX CRE) 1 SRS, 1 OCP

5 2 IPA 1.5 Nm/deg MIN transmission error (MIN CRE) 1 SRS, 1 OCP

6 1 IPA bearing t-bar MAX transmission error (MAX CRE) * OCP

7 1 IPA bearing t-bar MIN transmission error (MIN CRE) * OCP

8 1 IPA bearing t-bar 1.5 Nm/deg MAX transmission error (MAX CRE) * OCP

9 1 IPA bearing t-bar 1.5 Nm/deg MIN transmission error (MIN CRE) * OCP

10 1 YOKE MIN OD RATTLE

11 1 YOKE MAX OD RATTLE

12 1 YOKE MIN OD and MIN o-ring grooves SRS

13 1 YOKE MAX OD and MIN o-ring grooves SRS

14 1 YOKE MAX OD and MAX o-ring grooves SRS

15 1 YOKE MIN OD and MAX o-ring grooves SRS

16 2 Y- SPRING MAX rate 1 RATTLE, 1 SRS

17 2 Y- SPRING MIN rate 1 RATTLE, 1 SRS

18 1 TSC MAX IS bearing DIA (same as in sealing) and nominal (zero) concentricity BUZZ

19 2 PH MAX yoke bore 1 RATTLE, 1 SRS

20 2 PH MIN yoke bore 1 RATTLE, 1 SRS

21 1 PH NOMINAL (zero) concentricity IPA bores BUZZ

9

Parameter Design Leads

O NVH

1.Tonality / Running noise – DFSS project

2.Rattle

3.Clunk

4.Buzz

O Vacuum/pressure Leak test

Correlate leak rate to water leak paths by exploring test media (i.e. air,H2, Helium,

ultrasonic, etc) and parameters to create a dependable production test

O Friction

Including belt tensioning procedure for a capable production process

O SRS – DFSS project

O On center precision – DFSS project 10

Bayesian Prediction (method under investigation)

11

Bayesian reliability prediction for 68 mm steering gear is

98.1%R @ 50%C

= 1 part failing in 53

Likewise for 79 mm steering gear

97.1%R @ 50%C

= 1 part failing in 34

Combined reliability prediction for both is

98.8%R @ 50%C

= 1 part failing in 83 & is based on 51 parts tested

Seems a more reasonable value based on the limited number of parts tested

PROBLEM:

Model has not yet achieved universal acceptance

REDPEPR PROCESS (Ford tool)

12