Ride Quality Index A New Approach to Quantifying the Comparison of Acceleration Responses of High Speed Craft

Transcription

1 Ride Quality Index New pproach to Quantifying the Comparison of cceleration Responses of High Speed Craft Multi-gency Craft Conference Virginia Beach, Virginia 4 6 June 2 Michael Riley, Dr. Tim Coats Kelly Haupt, Don Jacobson distribution distribution unlimited is unlimited

2 Report Documentation Page Form pproved OMB No Public reporting burden for the collection of information is estimated to average hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 25 Jefferson Davis Highway, Suite 24, rlington V Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.. REPORT DTE JUN 2 2. REPORT TYPE 3. DTES COVERED --2 to TITLE ND SUBTITLE Ride Quality Index- New pproach To Quantifying The Comparison Of cceleration Responses Of High Speed Craft 5a. CONTRCT NUMBER 5b. GRNT NUMBER 5c. PROGRM ELEMENT NUMBER 6. UTHOR(S) 5d. PROJECT NUMBER 5e. TSK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGNIZTION NME(S) ND DDRESS(ES) NVSE Warfare Centers, Carderock,West Bethesda,MD, PERFORMING ORGNIZTION REPORT NUMBER 9. SPONSORING/MONITORING GENCY NME(S) ND DDRESS(ES). SPONSOR/MONITOR S CRONYM(S) 2. DISTRIBUTION/VILBILITY STTEMENT pproved for public release; distribution unlimited. SPONSOR/MONITOR S REPORT NUMBER(S) 3. SUPPLEMENTRY NOTES Presented during the Multi-gency Craft Conference (MCC) 2, June 4-6, 2,Joint Expeditionary Base, Fort Story-Little Creek, Virginia Beach, V 4. BSTRCT 5. SUBJECT TERMS 6. SECURITY CLSSIFICTION OF: 7. LIMITTION OF BSTRCT a. REPORT unclassified b. BSTRCT unclassified c. THIS PGE unclassified Same as Report (SR) 8. NUMBER OF PGES 23 9a. NME OF RESPONSIBLE PERSON Standard Form 298 (Rev. 8-98) Prescribed by NSI Std Z39-8

3 Outline Background Objective Repeatable /n Calculations Ride Quality Index Wave Slam Damage Potential Example Comparisons Summary Dr. Paul Rispin ONR 33 2

4 Background Historical perspective (95 s early 97 s) Passenger comfort studies for airplanes, cars, trains Ride quality linked to vibrations, temperature, noise RMS acceleration values used to quantify vibration amplitudes pplied to displacement hulls, surface effect ships, hydrofoils NSWCCD mid-97 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

5 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

6 /n Calculation Process Unambiguous statistical calculations Step Compute spectrum of unfiltered record Step 2 pply Hz low pass filter and compute RMS Use spectrum to confirm Hz filter criteria and ½ second time criteria RMS =.62 g Step 4 Compute statistical values Step 3 Extract peaks with PKT algorithm using RMS vertical threshold and ½-second time threshold 5.3g = / 3.48g = / 2.4g = /3.62g = RMS 5

7 l "E WRFRE CENTERS Carderock verage /n ccelerations -~ 2 Q c: +J :::::J.c... +J - 8 en 6 c Q) > +J ~ 4-2 = 3.48 g :::::J 6. E :::::J = 5.3 g Cl I: ::::: 4. "'... ~ < 3. u <( ~ 2. "' < a... I = 3.4a=g] ~/3 = 2.4 g. L--_~==~ Peak Number ~== 5=~ ~_j Peak cceleration (g) Combatant Craft Division

8 Filtered vs Unfiltered Wave Encounters Estimated rigid body acceleration 7

9 Single Impact Sequence of Events Time Response to B Close to gravity free-fall (-.9 g) Estimate of drop height prior to impact B B to C Maximum downward velocity Time of initial water impact Craft moving down in water Maximum loading phase Wave slam period C Time of maximum downward motion Instantaneous velocity = Loading reduced to ambient forces C to D Upward hydro-dynamic force Upward buoyant force Upward thrust vector Force upward stops at D D E B C 8

10 Peak cceleration Comparison 6 Peak cceleration (g) Condition I Condition II Peak Number Test Condition Variables: different craft, speeds, wave heights, gage locations

11 Different Comparison Format Peak cceleration (g) Condition II cceleration (g) Condition I Peak Number 2 y =.6846x Condition I Peak cceleration (g) The least squares linear fit has a zero intercept

12 l "E WRFRE CENTERS Carderock Ride Quality Index -') -s::::: -~ a.. Q) - Q) u <( s::::: :!::::: "C s::::: u 4 ~------~------~------~----~,~------~----~ 3 I Worse Ride Quality " ","" " " " ",",,,,' " " " " " y =.6846x RQI =.32 2 ~------~----~-- ~------~ ~4-~----~------~ " " Better I ~----~-- ~~=---~ ~ ~ ,.,-- Ride Quality ; ; " " " " ~ ~------~------~------~------~------~ Condition I Peak cceleration (g) Ride Quality Index (RQI) = - conditionii \ conditionl Combatant Craft Division

13 Why cceleration Ratio? Damage Categories Structural Damage Equipment malfunction or failure Crew discomfort or injury Damage Potential Shock Rigid Body Velocity RBII RBI V t RBII RBII V t RBI RBI If t i is relatively constant... then II I V V RBII RBI RQI VII V II I I Damage Potential 2

14 Ride Quality Index = f (Damage potential ) - Condition II cceleration (g) Ride Quality Y =.5x RQI = -.5 Index RQI y =.6846x RQI = Condition I Peak cceleration (g) ConditionII ConditionI Y =.25x RQI =.75 II I Damage Potential RQI II I Damage Potential RQI 3

15 RQI vs cceleration Ratio RQI = +.6 means 6% less than baseline (better ride) RQI Better Ride Same II I Worse Ride RQI = -.6 means 6% greater than baseline (worse ride) 4

16 Ride Quality Index Using /n Ratios Condition II Peak ccelerations (g) Worse Ride Better Ride y =.6846x RQI = Condition I Peak ccelerations (g) RQI / RMS /3 / / / II / I 4 Test Condition I Condition II Ride Quality Index / 5.3 g 3.5 g.34 / 3.48 g 2.82 g.9 /3 2.4 g.87 g.24 RMS.62g.54g.3 -Slope na na.29 Condition II cceleration (g) 3 2 y =.749x RQI = Condition I cceleration (g) 5

17 Simple Damage Mechanisms Cumulative Distribution (%) /3 = 2.4 g / = 3.48 g / = 5.3 g Test Condition I Condition II Ride Quality Index / 5.3 g 3.5 g.34 / 3.48 g 2.82 g.9 /3 2.4 g.87 g.24 RMS.62g.54g.3 -Slope na na.29 Peak cceleration (g) Failures due to cyclic lower amplitude wave slams (shock) could be caused by electrical disconnects of plugs, sockets, or circuit cards Failures due to severe (large amplitude) wave slams (shocks) could be caused by material over stresses or disconnects 6

18 Example: Same Craft Different Headings Peak Vertical cceleration (g) Quartering 33.7 knots Port beam 35 knots Port bow 26. knots Stern 33.3 knots RMS /3 / / y =.965x RQI =.4 y =.48x RQI =.58 y =.35x RQI = Head Sea 27.8 knots LCG Peak Vertical cceleration (g) y =.359x RQI =.64 7

19 Example: Same Craft Different Gage Locations Peak ccelerations (g) Bow Helm Stern RMS /3 / / y = x RQI = -.22 y =.328x RQI = -.3 y =.939x RQI = LCG Peak cceleration (g) 8

20 Example: Two Craft - Ride Control Comparison Ride Control cceleration LCG (g) Speed + x Speed y =.65x RQI =.35 y =.4442x RQI = No Ride Control cceleration LCG (g) 9

21 Observations Use of RQI requires consistent data processing Generalized /n process New approach Use of all peak accelerations Or, use of all statistics (RMS, /3, /, / ), not one level lso 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 /n process used 2

22 Summary pplied a 4-step computational process for repeatable /n calculations Introduced a simple Ride Quality Index New combined use of all peaks, RMS, /3, /, / 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 /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 2

23 l "E WRFRE CENTERS Carderock Questions ,--- j , _.~ , & ~ Qj Worse,.. "...::-/.,. _ t J Ride Quality ' _...,..,..._.----:c_..-~ Y =---+~ ,--I <{ ' RQI ~ 32.4 Belter Ride Quality I Ride Quality Index (RQI) == - ' conditionii ~ conditionl Condition I Peak cceleration (g) 4 E! s:::::.q 3... ~ cu Cll u 2 c( s::::: s::::: (.) v RMS /3 / / v // // / y /' / / / // ~. 7 49x RQI = Condition I cceleration (g) 6 Test Cond ition I Condition II Ride Quality Index / 5.3 g 3.5g.34 / 3.48g 2.82 g.9 /3 2.4 g.87 g.24 RMS.62g.54g.3 -Siope na na.29 Combatant Craft Division 22