Ride Quality Index –A New Approach to Quantifying the … · 2012-02-28 · – Passenger comfort...

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Ride Quality Index – A New Approach to Quantifying the Comparison of Acceleration

Responses of High Speed Craft

Michael Riley, Dr. Tim CoatsKelly Haupt, Don Jacobson

Multi-Agency Craft ConferenceVirginia Beach, Virginia

14 – 16 June 2011


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1. REPORT DATE JUN 2011 2. REPORT TYPE

3. DATES COVERED 00-00-2011 to 00-00-2011

4. TITLE AND SUBTITLE Ride Quality Index-A New Approach To Quantifying The Comparison OfAcceleration Responses Of High Speed Craft

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6. AUTHOR(S) 5d. PROJECT NUMBER

5e. TASK NUMBER

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) NAVSEA Warfare Centers, Carderock,West Bethesda,MD,20817

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12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited

13. SUPPLEMENTARY NOTES Presented during the Multi-Agency Craft Conference (MACC) 2011, June 14-16, 2011,Joint ExpeditionaryBase, Fort Story-Little Creek, Virginia Beach, VA

14. ABSTRACT

15. SUBJECT TERMS

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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18


Outline

• Background• Objective• Repeatable A1/n Calculations• Ride Quality Index• Wave Slam Damage Potential • Example Comparisons• Summary

2

Dr. Paul RispinONR 331


Background

• Historical perspective (1950’s – early 1970’s)– Passenger comfort studies for airplanes, cars, trains– Ride quality linked to vibrations, temperature, noise– RMS acceleration values used to quantify vibration amplitudes– Applied to displacement hulls, surface effect ships, hydrofoils

• NSWCCD mid-1970’s: RMS values reported not applicable when craft motions include shocks or impulsive velocity changes – Dissatisfaction with general lack of ride quality data– Lack of fully satisfactory criteria for judging ride quality in rough

seas– No standard process for acquiring and processing data

3


Objective

To present a simplified approach to quantifying

ride quality when comparing wave impacts for

different craft, different sea states, different speeds,

or different gage locations.

4


A1/n Calculation ProcessUnambiguous statistical calculations

5

Use spectrumto confirm10 Hz filter criteriaand ½ second time criteria

RMS = 0.62 g

Step 1 Compute spectrum of unfiltered record Step 2 Apply 10 Hz low pass filter and compute RMS

Step 3 Extract peaks with PKT algorithm using RMS vertical threshold and ½-second time threshold

5.31g = A1/1003.48g = A1/102.41g = A1/30.62g = RMS

Step 4 Computestatistical values


Average A1/n Accelerations--Al "EA

.... -WARFARE CENTERS

Carderock

- 120 ~ Q -c: 100 0 +J :::::J

80 .c .... +J en 60 ·-c Q)

40 > +J ~

A1110 = 3.48 g - 20 :::::J

6.00 E A 11100 = 5.31 g

:::::J 0 0 0 1

Cl 5.00 - 2 3 4 5 6 I:

I A1110 = 3.4a=g]

~/3 = 2.41 g

0 :0:::: 4.00 "' .... ~

<11 3.00 u u <( ~ 2.00

Peak Acceleration (g)

"' <11 a.. 1.00

0.00 0

L--_~==~---------5-0 ________ 1_0_0 ____ ~==1 5=0~------2-0-0~_j Peak Number

Combatant Craft Division


Filtered vs Unfiltered Wave Encounters

7

Estimated rigid body acceleration

DISTRIBUTION STATEMENT A: Approved for Public Release; distribution is unlimited 8

Single Impact Sequence of Events

Time Response

A to B • Close to gravity free-fall (- 0.9 g)• Estimate of drop height prior to

impact

B • Maximum downward velocity• Time of initial water impact

B to C • Craft moving down in water• Maximum loading phase• Wave slam period

C • Time of maximum downward motion• Instantaneous velocity = 0• Loading reduced to ambient forces

C to D • Upward hydro-dynamic force• Upward buoyant force• Upward thrust vector • Force upward stops at D

A

BC

D

E


Peak Acceleration Comparison

0

1

2

3

4

5

6

0 25 50 75 100 125

Pea

k A

cce

lera

tio

n (

g)

Peak Number

Condition I

Condition II

Test Condition Variables: different craft, speeds, wave heights, gage locations


Different Comparison Format

10

0

1

2

3

4

5

6

0 25 50 75 100 125

Peak

Acc

eler

atio

n (g

)

Peak Number

Condition I

y = 0.6846x

0

1

2

3

4

0 1 2 3 4 5 6Con

ditio

n II

Acce

lera

tion

(g)

Condition I Peak Acceleration (g)

The least squares linear fit has a zero intercept


Ride Quality Index

11

--Al "EA


Carderock

-0') -s::::: 0 -~ a.. Q) -Q) u u <(

s::::: 0

:!::::: "C

s::::: 0 u

4 ~------~------~------~----~,~------~----~ ,

I Worse 3 Ride Quality

" "

" ," ,"

" " " "

" " " " "

, , ,'

y = 0.6846x RQI = 0.32

2 ~------~----~-- ~------~~4-~----~------~-------1

1

" "

1 Better I ~----~--~~=---~------+-~ ~-+-------1

,.,-- Ride Quality

; ; "

" " " 0 ~--------~------~------~------~------~------~

0 1 2 3 4 5 6


Ride Quality Index (RQI) = 1- A Aconditionii

1\ Aconditionl



Why “Acceleration Ratio” ?

12

Damage Categories

Structural DamageEquipment malfunction or failure

Crew discomfort or injury

VelocityBodyRigidPotentialDamageShock

.constant..relativelyistIf iRBI

RBII

I

II

V

V

A

Athen

PotentialDamageV

V

A

ARQI

I

II

I

II 111

RBI

RBI

RBII

RBII

RBI

RBII

t

V

t

V

A

A


Ride Quality Index = f (Damage potential )-1

13

y = 0.6846xRQI = 0.32

0

1

2

3

4

0 1 2 3 4 5 6

Con

ditio

n II

Acce

lera

tion

(g)


Y = 0.25xRQI = 0.75

RQIPotentialDamageA

A

I

II RQIPotentialDamageA

A

I

II

ICondition

IICondition

A

ARQIIndexQualityRide

1

Y = 1.50xRQI = -0.5


RQI vs Acceleration Ratio

14

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 0.5 1 1.5 2 2.5I

II

AA

RQI

RQI = +0.6 means 60% less than baseline (better ride)

RQI = - 0.60 means 60% greater than baseline (worse ride)

BetterRide

WorseRide

Same


Ride Quality Index Using A1/n Ratios

15

y = 0.6846xRQI = 0.32

0

1

2

3

4

0 1 2 3 4 5 6

Cond

itio

n II

Peak

Acc

eler

atio

ns (g

)

Condition I Peak Accelerations (g)

Worse Ride

Better Ride

y = 0.7149xRQI = 0.29

0

1

2

3

4

0 1 2 3 4 5 6

Con

ditio

n II

Acce

lera

tion

(g)

Condition I Acceleration (g)

RMS A 1/3 A 1/10 A 1/100

0

01

10/1

10/1

10/1

I

II

A

ARQI

Test Condition I Condition IIRide Quality

Index

A 1/100 5.31 g 3.50 g 0.34

A 1/10 3.48 g 2.82 g 0.19

A 1/3 2.41 g 1.87 g 0.24

RMS 0.62g 0.54g 0.13

1-Slope na na 0.29


Simple Damage Mechanisms

16

0

20

40

60

80

100

120

0 1 2 3 4 5 6Cum

ulat

ive

Dis

trib

utio

n (%

)

Peak Acceleration (g)

A 1/100 = 5.31 g

A1/10 = 3.48 g

A1/3 = 2.41 g

Failures due to severe (large amplitude) wave slams (shocks) could be caused by material over stresses or disconnectsFailures due to cyclic lower amplitude

wave slams (shock) could be caused by electrical disconnects of plugs, sockets, or circuit cards

Test Condition I Condition IIRide Quality

Index

A 1/100 5.31 g 3.50 g 0.34

A 1/10 3.48 g 2.82 g 0.19

A 1/3 2.41 g 1.87 g 0.24

RMS 0.62g 0.54g 0.13

1-Slope na na 0.29


Example: Same Craft Different Headings

17

y = 0.351xRQI = 0.65

y = 0.9615xRQI = 0.04

y = 0.418xRQI = 0.58

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7

Peak

Ver

tical

Acc

eler

atio

n (g

)

Head Sea 27.8 knots LCG Peak Vertical Acceleration (g)

RMS A 1/3 A 1/10 A 1/100

Quartering 33.7 knots

Port beam 35 knots

Port bow 26.1 knots

Stern 33.3 knots

y = 0.359xRQI = 0.64


Example: Same Craft Different Gage Locations

18

y = 2.2244xRQI = - 1.22

y = 0.9319xRQI = + 0.07

y = 1.0328xRQI = - 0.03

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5 6 7

Peak

Acc

eler

atio

ns (g

)

LCG Peak Acceleration (g)

RMS A 1/3 A1/10 A 1/100

Bow

Helm

Stern


Example: Two Craft - Ride Control Comparison

19

y = 0.651xRQI = 0.35

y = 0.4442xRQI = 0.56

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 2 4 6 8Rid

e C

ontr

ol A

ccel

erat

ion

LCG

(g)

No Ride Control Acceleration LCG (g)

Speed A + x

Speed A


Observations

• Use of RQI requires consistent data processing– Generalized A1/n process

• New approach– Use of all peak accelerations – Or, use of all statistics (RMS, A1/3, A1/10, A1/100), not one level

• Also applicable to pitch, roll, pitch or roll rates

• Useful to quantify a skilled operators perception

• Compare craft responses regardless of the source of the data, when generalized A1/n process used

20


Summary

• Applied a 4-step computational process for repeatable A1/n calculations

• Introduced a simple Ride Quality Index– New combined use of all peaks, RMS, A1/3, A1/10, A1/100

– Proportional to wave slam (shock ) damage potential– Cumulative damage or single-severe slam affects– Useful tool for better/worse ride quality comparisons

• Use of standardized A1/n calculation and RQI may foster future comparisons of ride quality of different craft or different test conditions regardless of the source of the data

21


Questions

22

--Al "EA


Carderock

.2 4 -----,---j -----.-------.----__ ----,_.~-----.------,

& ~ Qj Worse , .. " ... ::-/ _ _.,. § 3 ------J Ride Quality '-----+--_...,..,._ t-----____ .._.----:c_..-~Y =-0--+~8-4-6,--I

<{ ' .--..-•· • RQI ~ 0 32 .4

4

E! s::::: .Q 3 .... ~ cu Cll u u 2 c(

s::::: 0

® 1 s::::: 0 (.)

0

v

0

Belter Ride Quality I


RMS A 1/3 A 1/10 A 1/100

// / /

• /

/ y ~ 0 . 71 49x

/' RQI = 0.29

//

//

v

3 4 5

Condition I Acceleration (g)


Ride Quality Index (RQI) == 1- 1'1 Aconditionii

~ Aconditionl

Test Condition I Condition II Ride Quality

Index

A 1/100 5.31 g 3.50g 0.34

A 1/10 3.48g 2.82 g 0.19

A 1/3 2.41 g 1.87 g 0.24

RMS 0.62g 0.54g 0.13 6

1-Siope na na 0.29

Ride Quality Index –A New Approach to Quantifying the … · 2012-02-28 · – Passenger comfort...

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