AUTOMOTIVE MASS PROPERTIES ESTIMATION

AUTOMOTIVE MASS PROPERTIES ESTIMATIONBrian Paul Wiegand, PE

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 2010

AUTOMOTIVE MASS PROPERTIES ESTIMATION1

WHY AUTOMOTIVE MASS PROPERTIES?PERSONAL INTEREST WROTE SAWE PAPER, JOURNAL ARTICLESAE MEMBER, SEMINAR, PUBLICATIONSPERSONAL LIBRARY, TECH PAPERSSIGNIFICANCE FUEL ECONOMY, EMISSIONS, SAFETY, RIDEACCELERATION, BRAKING, MANEUVEREXPAND SAWE SCOPEAEROSPACE MASS PROPERTIESMARITIME MASS PROPERTIES

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 20102

WHY AUTOMOTIVE MASS PROPERTIES?

WELL, AS THE VU-GRAPH SAYS, ITS A MATTER OF PERSONAL INTEREST..SAWE PAPER, JOURNAL ARTICLE, SAE MEMBER, SEMINAR, PUBLICATIONS, PERSONAL LIBRARY, TECH PAPERS

AND, OF COURSE, MASS PROPERTIES HAS GREAT SIGNIFICANCE FOR AUTOMOTIVE PERFORMANCE.FUEL ECONOMY, EMISSIONS, RIDE, SAFETY, ACCELERATION, BRAKING, MANEUVER, WHICH IS PRETTY MUCH THE SAME FOR ALL VEHICLES...

AND LAST, BUT NOT LEAST, WRITING A PAPER ON THIS SUBJECT SEEMED TO BE A GOOD WAY TO HELP EXPAND THE SCOPE OF OUR SOCIETY. I UNDERSTAND THAT AS A SOCIETY WE ARE INTERESTED IN BECOMING MORE INCLUSIVE, EXPANDING OUR MEMBERSHIP BASE, AND THIS IS MY SMALL WAY OF CONTRIBUTING TO THAT GOAL. THERE ARE ONLY ABOUT 40 PAPERS IN THE SAWE CATEGORY 31.0, AND NONE OF THOSE ADDRESS THE ESTIMATION OF AUTOMOTIVE MASS PROPERTIES FROM A TOP DOWN PARAMETRIC APPROACH. THE VAST MAJORITY OF OUR PAPERS AND JOURNAL TOPICS, ETC., CONCERN AEROSPACE AND MARITIME MATTERS.

2

NEED FOR AUTOMOTIVE MASS PROPERTIES ESTIMATION METHODOLOGY INDEPENDENT DESIGNERSSMALL, START-UP COMPANIES: APTERA MOTORS, MILNER MOTORS, FISKER AUTOMOTIVE, PANOZ AUTOMOTIVE DEVELOPMENT COMPANY, FUTURE VEHICLE TECHNOLOGIES, VECTOR MOTORS, TESLA MOTORS, ETC.KIT CAR, HOT ROD, CUSTOM CAR INDUSTRY: FIBERFAB US, FOOSH DESIGN, ROSSION AUTOMOTIVE, ETC.DESIGN CONSULTANTS: ENGINEERING DESIGN CONSULTANTS LTD, GORDON MURRAY DESIGN LTD, TECHNICAL ENGINEERING CONSULTANTS INC, ETC.RESEARCHERSALLEN, ROSENTHAL,& SZOSTAK; STEADY STATE AND TRANSIENT ANALYSIS OF GROUND VEHICLE HANDLING, 1987.LARRABEE & HAWKS, THE CALCULATED EFFECT OF CROSS-WIND GRADIENTS ON THE DISTURBANCE OF AUTOMOTIVE VEHICLES, 1969.SIMULATION PROGRAMMERSREALISTIC COMPUTER GAMING: GRAND THEFT AUTO, ROBOT AUTO RACING SIMULATOR (RARS), GRAND PRIX LEGENDS, ETC.VIRTUAL REALITY: VRDS (VIRTUAL REALITY DRIVING SIMULATOR) TO ASSESS BRAIN INJURY, PREVENT ALCOHOL ABUSE, DRIVERS EDUCATION, ETC.MOVIE SCENES: CARS (PIXAR, DISNEY), SPEED RACER (WARNER BROS), THE DARK KNIGHT (WARNER, LEGENDARY PICTURES), ETC.ACCIDENT INVESTIGATORSACCIDENT RESEARCH ENGINEERS INC, CRASH DATA SERVICES LLC, BISON FORENSIC ENGINEERS, ETC.

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 20103

AND THERE IS ANOTHER REASON FOR DOING THIS, AND THAT IS I THINK THAT A COMPREHENSIVE AUTOMOTIVE MASS PROPERTIES ESTIMATION METHODOLOGY WOULD HAVE A CERTAIN USEFULNESS. I IMAGINE THAT THE BIG ESTABLISHED AUTOMOTIVE MANUFACTURERS HAVE THEIR OWN MEANS OF ESTIMATING AUTOMOTIVE MASS PROPERTIES, WHICH THEY APPARENTLY ARE NOT SHARING, BUT THERE ARE INDEPENDENT DESIGNERS, RESEARCHERS, SIMULATION PROGRAMMERS, AND ACCIDENT INVESTIGATORS. 3

ESTIMATION METHODOLOGY LITERATURE SEARCHBOOKSBOSCH AUTOMOTIVE HANDBOOK, MECHANICS OF VEHICLES, THE AUTOMOTIVE CHASSIS, HANDBOOK OF VEHICLE DESIGN ANALYSIS, ETC.MAGAZINESAUTOMOTIVE ENGINEERING (SAE), ROAD & TRACK, THE AUTOMOBILE, MOTOR TREND, CAR AND DRIVER, ETC.PAPERSFUNCTIONAL DERIVATION OF VEHICLE PARAMETERS FOR DYNAMIC STUDIES, NATIONAL RESEARCH COUNCIL CANADA.DEVELOPMENTS IN CENTER OF GRAVITY AND INERTIAL ESTIMATION AND MEASUREMENT, SAE.TYPICAL VEHICLE PARAMETERS FOR DYNAMICS STUDIES REVISED FOR THE 1980S, SAE.ETC.

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 20104

TO START THE QUEST FOR A AUTOMOTIVE MASS PROPERTIES ESTIMATION METHODOLOGY I BEGAN WITH A LITERATURE SEARCH TO SEE WHAT WAS ALREADY AVAILABLE, WHICH I INTENDED TO BUILD UPON. WHAT I FOUND WAS THAT THERE REALLY ISNT VERY MUCH, AT LEAST BY WAY OF A COMPREHENSIVE, RELIABLE, ACCURATE METHODOLOGY. THERE ARE BITS AND PIECES OF WHAT COULD BECOME SUCH A METHODOLOGY IF DEVELOPED AND COMBINED APPROPRIATELY, AND I INCORPORATED WHAT I FOUND THAT WAS USEFUL INTO MY PAPER, WITH PROPER ATTRIBUTION, AS WE SHALL SEE.

THE SORT OF LITERATURE I WENT THROUGH IS LISTED IN THE VU-GRAPH. THE BOOKS CAME MAINLY OUT OF MY OWN PERSONAL LIBRARY, AND THE MAGAZINE ARTICLES WERE MAINLY ONES THAT I HAD COLLECTED OVER MANY YEARS. TECHNICAL PAPERS, HOWEVER, CAME FROM A NUMBER OF INTERNET SOURCES BUT MAINLY FROM THE SAE. YOU WOULD THINK THAT THE SAE WOULD HAVE A GREAT MANY PAPERS ON THIS SUBJECT, SO MANY AS TO RENDER THE CREATION OF A PAPER LIKE MINE REDUNDANT, BUT YOU WOULD BE WRONG. THERE IS ONLY A HANDFUL OF PAPERS THAT ATTEMPT A PARAMETRIC ESTIMATION OF AUTOMOTIVE MASS PROPERTIES, AND THOSE PAPERS TEND TO BE AS INCOMPLETE AND UNRELIABLE AS ANY OTHER PUBLICALLY AVAILABLE SOURCE, AS ILL ILLUSTRATE A LITTLE IN THE COURSE OF THIS PRESENTATION AND AS DISCUSSED AT LENGTH IN MY PAPER. 4

LITERATURE SEARCH RESULTNO EXISTING COMPREHENSIVE TOP-DOWN AUTOMOTIVE MASS PROPERTIES ESTIMATION METHODOLOGYAUTOMOTIVE DATA FOR DEVELOPMENT OF METHODOLOGY VERY LIMITED EXISTING METHODOLOGY ANALYSIS DEFICIENTDATA NOT NORMALIZED FOR TYPE, CONFIGURATION, WEIGHT CONDITION, SPEC/REGULATION, LEVEL OF TECHNOLOGYFORCED 0,0 INTERCEPTMISCONCEPTIONSTHE CENTER OF GRAVITY ISPROPERTY OF A GIVEN CAR AND CAN NOT BE READILY ESTIMATEDNO CORRELATION WITH ANY MEASURED VEHICLE PROPERTIES THAT WOULD ALLOW(Pxz)TO BE ESTIMATED

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 20105

SO, THE LITERATURE SEARCH TURNED UP SOME USEFUL THINGS, BUT NO EXISTING COMPREHENSIVE ESTIMATION METHODOLOGY. THERE WERE ATTEMPTS TO DEVELOP METHODS FOR ESTIMATION OF CERTAIN AUTOMOTIVE MASS PROPERTIES, BUT THE RESULTS WERE USUALLY NOT SATISFACTORY, AT LEAST NOT BY THE STANDARDS THAT WE WOULD APPLY.

MOST OF THE DIFFICULTY SEEMED TO STEM FROM THE FACT THAT THE AVAILABILITY OF APPROPRIATE AUTOMOTIVE DATA FOR THE DEVELOPMENT OF SUCH A METHODOLOGY WAS VERY LIMITED. THIS NEED FOR DATA MAY HAVE BEEN THE REASON BEHIND THE DEFICIENTCIES OBSERVED OF EXISTING ATTEMPTS: IT MAY BE WHY DATA WAS NOT NORMALIZED FOR VEHICLE TYPE, CONFIGURATION, WEIGHT CONDITION, APPLICABLE SPEC/REGULATION, OR LEVEL OF TECHNOLOGY; AND WHY THE EQUATIONS RESULTING FROM REGRESSION ANALYSIS WERE OFTEN FORCED TO GO THROUGH THE 0,0 POINT. IT WAS A MATTER OF DESPERATION FOR DATA, AND THE RESULTANT FEELING SEEMED TO BE THAT ANY DATA IS GOOD; JUST THROW IT ALL IN TOGETHER AND THE VARIETY WILL MAKE THE RESULTING ESTIMATION ROUTINE MORE ROBUST. AND 0,0 WAS ONE MORE DATA POINT..

THEN THERE ARE SOME OTHER MISCONCEPTIONS. THERE SEEMED TO BE A CERTAIN DISPAIR ON THE PART OF SOME AUTHORS THAT CERTAIN MASS PROPERTIES COULD BE ESTIMATED WITH ANY DEGREE OF ACCURACY REGARDLESS OF AMOUNT OF DATA AVAILABLE. THE PROBLEM SEEMED TO BE THAT PARAMETERS LIKE WHEELBASE, HEIGHT, WIDTH, TRACK, ETC., WERE EXTERNAL MEASUREMENTS; BUT MASS PROPERTIES LIKE THE CENTER OF GRAVITY AND INERTIAS WERE DETERMINED BY THE INTERNAL ARRANGEMENT OF THE COMPONENT MASSES. OF COURSE, NORMALIZING THE DATA SO THAT IT CONFORMS TO A SPECIFIC AUTOMOTIVE PARADIGM: PASSENGER CAR, FWD, FRONT ENGINE, US SPEC, CURB WEIGHT CONDITION, ETC. IN THAT WAY THE INTERNAL ARRANGEMENT OF THE COMPONENT MASSES IS ACCOUNTED FOR, ALTHOUGH IN A GENERAL WAY. THEN THE MEASURED EXTERNAL PARAMETERS CAN PROVIDE CLUES AS TO THE SPECIFIC MASS PROPERTY VALUES..

IN SHORT, WHATS OUT THERE BY WAY OF AUTOMOTIVE MASS PROPERTIES ESTIMATION WOULD BE A LOT BETTER IF IT HAD BEEN DONE BY WEIGHT ENGINEERS, NOT PEOPLE FROM OTHER DISCIPLINES TRYING TO DO A MASS PROPERTIES TASK.5

AUTOMOTIVE MASS PROPERTIES ESTIMATION METHODOLOGY DEVELOPMENT

COMPREHENSIVETOTAL VEHICLE WEIGHT, C.G. COORDINATES, INERTIAS, PRODUCTS SPRUNG WEIGHT, C.G. COORDINATES, INERTIAS, PRODUCTSUNSPRUNG WEIGHT, C.G. COORDINATES, INERTIAS, PRODUCTSTOP-DOWNHIGH-LEVEL PARAMETER INPUT: VEHICLE LENGTH, WIDTH, HEIGHT, WHEELBASE, TRACKPROPER STATISTICAL ANALYSISAPPROPRIATE REGRESSION MODEL: LINEAR MULTI-VARIABLE, POWER MULTI-VARIABLE, ETC.FLOATING INTERCEPTNORMALIZED PASSENGER CAR DATABASES: FRONT ENGINE/RWD/1984 U.S. SPEC SPORT/SPORTY, FRONT ENGINE/FWD/85-95 U.S. SPEC SDN/CPE, FRONT ENGINE/RWD/76-88 U.S. SPEC SDN/CPE ANALYSIS RESULT SATISFACTORINESS: SAWE CRITERIA (WEIGHT ENGINEERS HANDBOOK PAGE 18.9); OTHER STATISTICAL INDICATORS: STANDARD ERROR, P-TEST, F-TEST, ETC. ADEQUATE DATA: NHTSA VIPMD, VARIOUS LITERATURE SOURCESCOMBINE WITH SELECT LITERATURE SEARCH RESULTSUNSPRUNG MASS PROPERTIES (COLIN CAMPBELL, MODIFIED) PRODUCT OF INERTIA (G.L. BASSO)69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 20106

So, I wanted to do something comprehensive, meaning.

And I wanted it to be top-down, meaning I wanted estimation routines requiring high-level parametric input: length, width, height, wheelbase, track as would be available early on in the design stage or as would be available from the common literature for existing vehicles..

To do this I would do a proper regression analysis: using most appropriate model(s), floating intercept, normalized database(s), and rational determination of satisfactoriness.All I needed was adequate data. Well, the NHTSA, as a result of the decades old debate on roll-over safety, began collecting vehicle track and C.G. Height data for the calculation of vehicle Static Stability Factors (SSFs = T/2Hcg), and that grew to include all the top level parameters and mass properties. The VIPMD has about 500 data items.

Integrated with the results of my analysis would be those useful results of the literature search: Campbell & Basso.

Colin Campbell is an engineer and the noted author of many books on automotive engineering.

G.L. Basso is someone about whom a good deal less is known; he is a researcher who has written or co-written a number of technical papers for the Canadian government: Functional Derivation of Vehicle Parameters for Dynamic Studies, National Research Council of Canada, 1974. 6

THE RESULTING MASS PROPERTIES ESTIMATION METHODOLOGY

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 20107USE THE TOP-LEVEL REGRESSION ANALYSIS DERIVED ESTIMATION ROUTINES TO DETERMINE THE TOTAL VEHICLE MASS PROPERTIES, AND USE THE MODIFIED COLIN CAMPBELL METHOD TO DETERMINE THE UNSPRUNG MASS PROPERTIES, THEN FIND THE SPRUNG MASS PROPERTIES VIA STANDARD WEIGHT ACCOUNTING PROCEDURE:

1995 Chevrolet Lumina:

Now, the way the resultant total mass estimation methodology of my paper works is illustrated by this vu-graph. The mass properties for the total vehicle: weight, cg, inertias, and products are estimated per the regression analysis formulae I developed plus Bassos equations (for the products). Then the unsprung vehicle mass properties are estimated via Colin Campbells method. Finally, the sprung vehicle mass properties result from the application of the normal weight accounting equations to subtract the unsprung mass properties from the total vehicle mass properties..7

SPRUNG MASS ROLL MOMENT OF INERTIA69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 20108 Iroll = Ixs Cos2 2 Pxzs Sin Cos + Izs Sin2 + Ws d2

Then the only thing left to do to make this methodology truly comprehensive in determining all the high-level vehicle mass properties is to determine the sprung mass inertia about the roll axis as shown.

Roll axis at distance d from, and some at some angle phi with respect to, the longitudinal reference axis. 8

ESTIMATION ROUTINES, VEHICLE(SAMPLE)Wt = - 15.3678 Loa 86.3740 Woa 3101.8312 Hoa + 870.3500 Wb - 2675.1199 Tf + 4963.0342 Tr + 343.9573 (Eq. 3.11) Lcg = 0.7354 Wb + 0.7287 Tf 1.0662 Tr + 0.0431 Loa 0.2256 Hoa - 0.4656 Woa 0.6321 (Eq. 5.6) Hcg = 0.1956 Wb 0.1954 Tf + 0.2150 Tr 0.0335 Loa + 2.1407 Hoa 0.1524 Woa 1.5109 (Eq. 5.13) Ix = 355.9595 Wt0.3340 Hoa-1.8351 Hcg4.1633 Tf-4.2664 Tr7.7809 Woa-0.4812 (Eq. 7.37) Iy = 0.6722 Wt0.6639 Wb8.5279 Loa0.9883 a-2.6097 Hoa-14.4677 Hcg2.0423 (Eq. 7.39) Iz = 1305.5048 Wt-1.1589 Wb11.1997 Loa-0.0403 Lcg-4.8950 Tf-3.7181 Tr9.3188 Woa-5.3959 (Eq. 7.41)Pxz = 0.0374 Wt2/3 Wt/g tan 2 (G. L. Basso) (Eq. 9.2)

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 2010

9

Now, just to give you an idea of what some the estimation routines look like, we include this vu-graph. This is just a sample, the paper literally has dozens of ways to calculate many specific mass properties, depending on what parameter input is available. Note we have one of G.L. Bassos contributions at the end there..9

CAMPBELL METHODOLOGY, UNSPRUNG WEIGHT69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 201010

1994 Ford Taurus:Frt: Wusf = (3237.3 x 0.0675 x 0.59) + (2 x 40.37) = 209.7 lb (95.1 kg) / axle Est., vs. 197.1 lb (89.5 kg)/ axle Act.Rr: Wusr = (3237.3 x 0.0530 x 0.59) + (2 x 40.37) = 182.0 lb (82.5 kg) / axle Est., vs. 195.1 lb (88.5 kg)/ axle Act.

Tire Weight TableWheel Weight Table APPENDIX D

Speaking of Bassos contributions, here is essentially Colin Campbells contribution to this methodology: the estimation of the unsprung mass properties.The 94 Ford Taurus is used as an example because the unsprung mass of this vehicle was determined empirically by two different methods, and then painstakingly calculated by yours truly; the results are all so closeIf there are any questions about this later I have a considerable number of back-up vu-graphs.

Anyway, as you can see the unsprung weight is determined by taking an appropriate coefficient for the type of suspension contemplated, multiplying by the vehicle (curb) weight, and adding in the weight of a set of wheels and tires. The weight of the wheels and tires may be approximated by finding something similar to what is wanted from the wheel and tire weight tables included in the paper, or very often the exact weight can be found for the specific items from an internet data search. Once the unsprung weight is determined the other unsprung mass properties can be estimated via some simple calculations as illustrated in my paper..10

HOW WELL ROUTINES WORK69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 201011

Plot of vertical cg variation for 10 Front Engine, RWD, US spec, 1985-1995 passenger cars

Jaroslav Taborek, Mechanics of Vehicles, Cleveland, OH; Machine Design, 1957. Eq. 5.7

Allen, Rosenthal, and Szostak, Steady State and Transient Analysis of Ground Vehicle Handling, Automotive Crash Avoidance Research, Warrendale, PA; SAE SP-699, 1987. Eq. 5.8Study of relative stability of various automotive configurations during cornering while undergoing acceleration or braking, Needed estimates of: Zcg, Ixxs, Izzs, Irolls to conduct dynamic simulations; backed by the NHTSA and the SAE and STILL HAD TO DEVELOP ESTMATION ROUTINES using an 18 vehicle database varying from: 1956 to 1980, economy car to motorhome, FWD to RWD to AWD.

Wiegand, 1 parameter (Hoa) linear regression analysis equation. Eq. 5.10

6 parameter (Wb, Tf, Tr, Loa, Hoa, Woa) linear multi-regression analysis equation. Eq. 5.1311

CONCLUSIONSA BASIS FOR A COMPREHENSIVE TOP- DOWN ESTIMATION OF AUTOMOTIVE MASS PROPERTIES HAS BEEN DEVELOPED AND PRESENTED BUTDUE TO THE INFINITE VARIATION IN AUTOMOTIVE TYPE, CONFIGURATION, SPECIFICATION/REGULATION, AND LEVEL OF TECHNOLOGY THERE IS INFINITE SCOPE FOR FURTHER DEVELOPMENT.

69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 201012

There are literally dozens of conclusions of various degree of significance in Chapter 10 of the paper, but this is essentially the conclusion from the 35,000 foot level, so to speak.12

Q&AFIVE MINUTES ARE ALLOCATED FOR ASKING QUESTIONS OF THE AUTHOR69TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Virginia Beach, VA, 22-26 May 201013

13

Colin Campbell, M.Sc., C. Eng, A.M.I. Mech.E., b. 1913 - d. n/a Senior Research Engineer, ICI LtdSenior Project Engineer, Walker Mfg. Co., Wisconsin, U.S.A.Managing Director, The Sports Car Garage, Blackburn, Lancaster, U.K.Technical Officer, Royal Aircraft Establishment, Farnborough, U.K.Author of Six (6) Books on Automotive Subjects69th Annual International Conference of the SAWE14

UNSPRUNG WEIGHT ESTIMATION The paper Developments in Vehicle Center of Gravity and Inertial Estimation and Measurement introduced a means by which the total vehicle unsprung weight may be empirically determined while the vehicle is on the VIMF (Vehicle Inertia Measurement Facility) test device. The method was applied to a 1994 Ford Taurus. In two tests, values of 150.5 kg (331.8 lb) and 177.4 kg (391.1 lb) were obtained for the unsprung weight. Then the Transportation Research Center in East Liberty, Ohio, tore the Taurus apart and weighed the unsprung mass (which would seem to require a good deal of judgment as some components are only to be considered partially unsprung!); resulting in a weight of 178 kg (392.4 lb), suggesting a possible error range for this measurement method of -18% to -0.3% (!).

69th Annual International Conference of the SAWE15

1994 FORD TAURUS UNSPRUNG WEIGHT CALCULATION69th Annual International Conference of the SAWE16

1994 FORD TAURUS UNSPRUNG WEIGHT CALCULATION (CONT)69th Annual International Conference of the SAWE17

UNSPRUNG WEIGHT ESTIMATION69th Annual International Conference of the SAWE18

G.L. BASSOWORKED FOR NATIONAL AERONAUTICAL ESTABLISHMENT LABORATORY, NATIONAL RESEARCH COUNCIL OF CANADA.WROTE REPORT LTR-ST-747, FUNCTIONAL DERIVATION OF VEHICLE PARAMETERS FOR DYNAMIC STUDIES, 1974.DERIVED METHODS FOR AUTOMOTIVE Pxz ESTIMATION.69th Annual International Conference of the SAWE19

BASSO Pxz ESTIMATION METHOD(S)69th Annual International Conference of the SAWE20

1960 MICHAEL COSTIN (LOTUS)69th Annual International Conference of the SAWE21