AUTOMOTIVE MASS PROPERTIES ESTIMATION

MASS PROPERTIES & AUTOMOTIVE LATERAL ACCELERATIONBrian Paul Wiegand, PE

70TH Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 2011

MASS PROPERTIES & AUTOMOTIVE LATERAL ACCELERATION1

WHY AUTOMOTIVE MASS PROPERTIES?PERSONAL INTEREST SAWE: WROTE PAPERS & JOURNAL ARTICLESSAE MEMBER: SEMINAR, PUBLICATIONSPERSONAL LIBRARY: BOOKS, TECH PAPERSSIGNIFICANCE ACCELERATION / BRAKING, MANEUVER, RIDEFUEL ECONOMY, EMISSIONS, SAFETYEXPAND SAWE SCOPEAEROSPACE MASS PROPERTIESMARITIME MASS PROPERTIES

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 20112

WHY AUTOMOTIVE MASS PROPERTIES?

WELL, AS THE VU-GRAPH SAYS, ITS A MATTER OF PERSONAL INTEREST..SAWE PAPER, JOURNAL ARTICLES, SAE MEMBER, SEMINAR, PUBLICATIONS, PERSONAL LIBRARY TECH BOOKS & 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; THE VAST MAJORITY OF OUR PAPERS AND JOURNAL TOPICS, ETC., CONCERN AEROSPACE AND MARITIME MATTERS.

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THE GRAND SCHEME ALL BASIC AUTOMOTIVE PERFORMANCE CAN BE DEVIDED INTO ONE OF THREE CATEGORIES:LONGITUDINAL: ACCELERATION & BRAKINGLATERAL: TURNING, ROLLOVER, DIRECTIONAL STABILITYVERTICAL: SHOCK, VIBRATION, PITCH & ROLL MOTION ALL OTHER AUTOMOTIVE ISSUES CAN BE RELATED TO THE ABOVE: FUEL ECONOMY / EMMISSIONS SAFETY: PASSIVE & ACTIVE NVH: NOISE, VIBRATION, & HARSHNESSTHEREFORE, THREE SAWE PAPERS:MASS PROPERTIES & AUTOMOTIVE LONGITUDINAL ACCELERATION, SAWE PAPER #1634, ATLANTA, GA, 21-23 MAY 1984.MASS PROPERTIES & AUTOMOTIVE LATERAL ACCELERATION, SAWE PAPER #3528, HOUSTON, TX, 14-19 MAY 2011.MASS PROPERTIES & AUTOMOTIVE VERTICAL ACCELERATION, SAWE PAPER #3521, HOUSTON, TX, 14-19 MAY 2011.AND A FOURTH SUPPORTING PAPER:AUTOMOTIVE MASS PROPERTIES ESTIMATION, SAWE PAPER #3490, VIRGINIA BEACH, VA, 22-26 MAY 2010.

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 20113

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MASS PROPERTIES & AUTOMOTIVE LATERAL ACCELERATIONTIRE BEHAVIORCOEF OF TRACTION, DRIFT ANGLEWEIGHT TRANSFERSLIDE & ROLLOVERTRANSIENT CONDITIONRISE & DECAY, CENTER OF OSCILLATION STEADY STATE CONDITIONOVERSTEER & UNDERSTEER DIRECTIONAL STABILITYSTATIC & DYNAMIC70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 20114

Airplane behavior is overwhelmingly dictated by aerodynamic forces, while automobile behavior is a matter of tire forces. However, even though the automobile preceded the airplane by nearly two decades the theory of automobile performance and control lagged that of the airplane by about 35 years. The Wright brothers built a wind tunnel to study aerodynamic effects before their first powered, manned flight in 1903. The first tire test machine was probably the rolling drum of Becker, Fromm, and Maruhn in 1930. The war years of WW I and WW II brought most automobile research to a halt, but only accelerated aircraft research. Although the genesis of automotive theory can be traced back to the 1920s, it was after WW II that there was an explosion of automobile theory which, to a large degree, was modeled after the airplane example.4

TIRE BEHAVIOR

70th Annual International Conference of the Society of Allied Weight Engineers, Inc. Houston, TX, 14-19 May 20115COEFFICIENT OF LATERAL TRACTION IS FUNCTION OF NORMAL LOAD: = b m NPARABOLIC NORMAL LOAD LATERAL FORCE RELATIONSHIP: F = N = (b m N)N = b N mN2

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TIRE BEHAVIOR LATERAL FORCE DRIFT ANGLE70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 20116

TIRE BEHAVIOR LATERAL FORCE DRIFT ANGLE70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 20117

TIRE BEHAVIOR NORMAL LOAD - LATERAL FORCE DRIFT ANGLE 70th Annual International Conference of the Society of Allied Weight Engineers, Inc. Houston, TX, 14-19 May 20118

WEIGHT TRANSFER

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 20119 Faxle= Fi + Fo = (b m Ni)Ni + (b m No)No

Ni= (Waxle /2) Waxle ay(hcg /t) No= (Waxle /2) + Waxle ay(hcg /t)

AFFECTS THE POTENTIAL LATERAL TRACTION AT AN AXLE:

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POTENTIAL LATERAL TRACTION vs. LATERAL FORCE @ AXLE

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201110TRACTION POTENTIAL:TRACTION REQUIRED:

SLIDE & ROLLOVER ACCELERATIONSPOINTS A (SLIDE) & C (ROLLOVER):70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201111

SLIDE & ROLLOVER ACCELERATIONS70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201112

SLIDE ACCELERATION (POTENTIAL TRACTION = REQUIRED TRACTION, POINT A):ROLLOVER ACCELERATION (WEIGHT TRANSFER = WEIGHT, POINT C):

MAXIMUM LATERAL ACCELERATION

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201113

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ROLLOVER 70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201114

+NHTSA NCAP ROLLOVER RESISTANCE RATING (1-5 STARS) BASED (WITH HEAVY SSF BIAS) ON:THE SSF IS EXACTLY EQUAL TO THE PREVIOUS ayoverturn EQUATION

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TWO AXLES, SPRUNG MODEL 70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201115

SPRUNG MASS ROLLS GEOMETRY CHANGES ROLL ANGLE x ROLL STIFFNESS = LATERAL FORCE x ROLL HEIGHT

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SPRUNG MODEL 70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201116 ROLL ANGLE x ROLL STIFFNESS = LATERAL FORCE x ROLL HEIGHT

FRONT AXLE: REAR AXLE:

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TRANSIENT CONDITION70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201117

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TRANSIENT CONDITION70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201118

THE OSCILLATION CENTER, THE INITIAL CENTER OF VEHICLE ROTATION, WHOSE LOCATION DEPENDS ON THE X FACTOR,WHICH IN TURN DEPENDS ON YAW RADIUS OF GYRATION & CG.

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STEADY STATE CONDITION70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201119

SKIDPAD FOR STEERING CHARACTER & MAXIMUM LATERAL ACCELERATION

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DIRECTIONAL STABILITY

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 2011

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DISTURBANCE RESPONSE

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DIRECTIONAL STABILITY

70th Annual International Conference of the Society of Allied Weight Engineers, Inc. Houston, TX, 14-19 May 2011

21 EXPLANATION:TRADITIONAL (pre-1956) STABILITY (STATIC)

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DIRECTIONAL STABILITY

70th Annual International Conference of the Society of Allied Weight Engineers, Inc. Houston, TX, 14-19 May 2011

22FROM THE GEOMETRY AND THE 2-D FREE BODY EQUATIONS OF MOTION FOR VEHICLE IN A STEADY STATE CONDITION: SUM LATERAL FORCES = 0, SUM MOMENTS ABOUT CG = 0.

THE SOLUTION YIELDS SOME INTERESTING INSIGHTS WHICH CAN BE ADJUSTED SOMEWHAT TO ACCOUNT FOR WEIGHT TRANSFER AND ROLL.BICYCLE MODEL, A MORE MODERN ANALYSIS:

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DIRECTIONAL STABILITY

70th Annual International Conference of the Society of Allied Weight Engineers, Inc. Houston, TX, 14-19 May 2011

23BICYCLE MODEL, SOME ANALYSIS RESULTS:

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CONCLUSIONSMAXIMUM LATERAL (SLIDE) ACCELERATIONROLLOVER ACCELERATIONTRANSIENT CONDITION STEADY STATE / STABILITY CONDITION

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201124FOUR MAJOR AREAS:

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.24

MAX LAT ACCEL CONCLUSIONS

MINIMIZE VEHICLE WEIGHT.LOCATE VEHICLE C.G. SO THERE IS EVEN STATIC WEIGHT/AREA LOAD ON ALL TIRES.MINIMIZE VEHICLE C.G. HEIGHT.MAXIMIZE VEHICLE TRACK.MAXIMIZE TIRE COEFFICIENT b, MINIMIZE TIRE COEFFICIENT m.MINIMIZE ROLL (MINIMIZE SPRUNG WEIGHT C.G. TO R.C. HEIGHT / MAXIMIZE ROLL STIFFNESS).MINIMIZE DIRECTIONAL STABILITY.

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201125

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.25

ROLLOVER ACCEL CONCLUSIONS

MINIMIZE VEHICLE C.G. HEIGHT.MAXIMIZE VEHICLE TRACK.MINIMIZE VEHICLE ROLL:MINIMIZE SPRUNG WEIGHT C.G. TO R.C. HEIGHTMAXIMIZE ROLL STIFFNESS.

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201126

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.26

TRANSIENT CONCLUSIONS

MINIMIZE ROLL INERTIA.MINIMIZE YAW INERTIA.MINIMIZE C.G. TO O.C. DISTANCE:MINIMIZE YAW RADIUS OF GYRATION.WEIGHT DISTRIBUTION AS CLOSE TO 50/50 AS POSSIBLE.

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201127

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.27

STABILITY CONCLUSIONS

MAXIMIZE WEIGHT (not recommended).MAXIMIXE YAW INERTIA (not recommended).UNDERSTEER:FRONT WEIGHT BIAS.REAR CORNERINING STIFFNESS BIAS.FRONT ROLL RESISTANCE BIAS.NOSE DOWN ROLL AXIS.

70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201128

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.28

Q&AFIVE MINUTES ARE ALLOCATED FOR ASKING QUESTIONS OF THE AUTHOR70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201129

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BACKUP RESERVE SLIDES IN ANTICIPATION OF QUESTIONS THAT MAY BE ASKED 70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201130

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STEERING GEOMETRY 70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201131

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DARWIN STEERING GEOMETRY 70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201132

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CONTACT AREA & LATERAL LOAD 70th Annual International Conference of the Society of Allied Weight Engineers, Inc.Houston, TX, 14-19 May 201133

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