Automotive Dynamics and Design 1: Introduction

AUTOMOTIVE DYNAMICS and DESIGN: SYLLABUS 1

AUTOMOTIVE DYNAMICS and DESIGN

Brian Paul Wiegand, B.M.E., P.E.


DYNAMICS WITHOUT AN UNDERSTANDING OF

VEHICLE

DYNAMICS THE MOST BEAUTIFUL DESIGN

IS BUT AN EMPTY SHELL


DESIGN WITHOUT A BEAUTIFUL DESIGN THE

DYNAMICS ARE WITHOUT SOUL


DYNAMICS, the TWO ASPECTS OF:KINEMATICS – THE STUDY OF THE

GEOMETRY OF MOTION:

KINETICS – THE STUDY OF FORCE, MASS, AND ACCERATION:


DYNAMICS, the KINETICS ASPECT:

NEWTON’S SECOND LAW

TRANSLATIONAL:

F = m aROTATIONAL:

T = I α


DYNANICS, MASS PROPERTIES SIGNIFICANCE :

BECAUSE DYNAMICS IS SO DEPENDENT ON MASS PROPERTIES AN ENTIRE ENGINEERING DISCIPLINE IS

DEVOTED TO… “MASS PROPERTIES ANALYSIS &

CONTROL”


DYNAMICS, the TEN MASS PROPERTIES:

1. WEIGHT, indirect measure of mass.2. X, longitudinal center of gravity

coordinate. 3. Y, lateral center of gravity coordinate. 4. Z, vertical center of gravity coordinate. 5. Ix , mass moment of inertia about

longitudinal axis.6. Iy , mass moment of inertia about the

lateral axis.7. Iz , mass moment of inertia about the

vertical axis.8. Pxy , measure of mass asymmetry in the

X-Y plane.9. Pxz , measure of mass asymmetry in the

X-Y plane.10. Pyz , measure of mass asymmetry in the

X-Y plane.


AUTOMOTIVE DYNAMICS, the ROLE of MASS PROPERTIES:

The mass properties of a vehicle affect its motion in all directions, translational and rotational.

Mass properties affect automotive longitudinal motion, automotive lateral motion, and automotive

vertical motion. Of course, lateral or longitudinal inputs can lead to vertical responses, and vice versa; every aspect of a vehicle’s dynamics is

interconnected with every other aspect, but it is convenient to divide up automotive dynamics

as if the subject were purely a matter of independent motions along and/or rotations about the longitudinal, lateral, and vertical

axes.


AUTOMOTIVE DYNAMICS, the MOTIONS and ROTATIONS:

1

2

3

4


AUTOMOTIVE DYNAMICS, THE THREE MAIN DIVISIONS:

AUTOMOTIVE LONGITUDINAL MOTION: ACCELERATION, BRAKING DECELERATION,

CRASH DECELERATION.AUTOMOTIVE LATERAL MOTION:

TRANSIENT & STEADY STATE LATERAL ACCELERATION, ROLLOVER, DIRECTIONAL STABILITY.

AUTOMOTIVE VERTICAL MOTION: ROAD SHOCK & VIBRATION, ROAD CONTACT, BOUNCE & PITCH RIDE MOTIONS.


AUTOMOTIVE DYNAMICS, LONGITUDINAL MOTION DETAILS :

ACCELERATION: Ft = me a, “me” = Effective Mass, “Ft” = Total Drive Force (Traction – Roll Resistance – Aero Drag), No Direct Analytical Solution but Numerical Computer Program Solution (MAXGLONG.BAS). BRAKING: Ft d = ½ me V2, “Ft” =Total Resistance Force (Traction + Roll Resistance + Aero Drag) × Stopping Distance “d” = “Work”. “½ me V2” = “Kinetic Energy”. No Direct Analytical Solution but Numerical Computer Program Solution (MAXDLONG.BAS). CRASH (Full Front/Rear Only): F = me a / Ft d = ½ me V2 / F δt = me ΔV, “me” Modified by Shedding of Mass / Incapacitation of Drivetrain / Loss of Traction / Miscellaneous Energy Losses. Human Physical Characteristics Establish the Design Boundaries, But Automotive Crash Characteristics Establish the Design Reality. Historical Background, Human Injury Criteria and FMVSS / NCAP. Use of Force vs. Deformation Function Graphics and Equations plus Impulse-Momentum Equations to Solve Simple Co-Linear Front/Rear Crash Problems, Computer Program Solution (TBD). CASE HISTORIES: 1958 Jaguar XK150S, 1996 Dodge Neon, 2006 Honda Ridgeline.


AUTOMOTIVE DYNAMICS, LATERAL MOTION DETAILS:

GENERAL PLANE MOTION: Automobile in Maneuver, Transient and Steady State Conditions.

TIRE BEHAVIOR: Lateral Force Generation, “Slip” Angle, Pneumatic Trail, Self-Aligning Torque.

LATERAL “WEIGHT TRANSFER”:Slide and Rollover Accelerations at an Axle. LONGITUDINAL WEIGHT DISTRIBUTION: The “Ideal” Weight Distribution Between

Axles. LONGITUDINAL “WEIGHT TRANSFER”: Sprung Model, Sprung and Unsprung Mass, Roll

Stiffness, Roll Gain, Over/Under Steer. TRANSIENT CONDITION: Yaw Response Time = Rise Time + Decay Time, Slalom Test,

Yaw Radius of Gyration, Dynamic Index in Yaw, Instantaneous Center of Yaw, Yaw Inertia About the Instantaneous Center.

STEADY STATE CONDITION: Skidpad, Maximum Lateral Acceleration, Over/Neutral/Under Steer.

ROLLOVER: NHTSA NCAP Vehicle Rating by Static Stability Factor (SSF) and Dynamic “Fishhook Test”, Safety (Rollover and Roof Crush).

DIRECTIONAL STABILITY: Historical Background, Static and Dynamic Stability, Lateral Disturbances (Road, Wind Gust) to Longitudinal Motion, Over/Neutral/Under Steer Reaction, Simple “Bicycle” Stability Model, Steering Geometry, Understeer Coefficient, Characteristic Speed, Critical Speed, Steering Angle, Static Margin.

CASE HISTORIES: 1980 Ford Fiesta S.


AUTOMOTIVE DYNAMICS, VERTICAL MOTION DETAILS: HUMAN PHYSIOLOGY: Establishes Shock and Vibration Goals. ROAD SHOCK: Unsprung and Sprung Suspension Models – 1

DOF / 2 DOF, Unsprung and Sprung Frequencies – Bump / Dip / Hop, Spring Stiffness – Series / Parallel / Effective, Solutions – Approximate / Intermediate / Exact, Damping, Wheel Size – Rigid vs. Pneumatic Tire.

ROAD CONTACT: Dip “l” and “d” Parameters. ROAD VIBRATION: Road Input to Suspension System /

Suspension System Output to Sprung Mass, Road Power Spectral Density, Gain Factors – Road / Unsprung / Sprung.

RIDE MOTIONS: Bounce and Pitch, Dynamic Index in Pitch (DIP), Coupled (Beat) Motion and Uncoupled Motion, Coupling Coefficient, Principal Modes – Frequencies and Nodes, Spring Center, Conjugate Centers, Olley’s Rules – Flat Ride.

CASE HISTORIES: 1958 Jaguar XK150S, 1980 Ford Fiesta S


AUTOMOTIVE DYNAMICS, AUXILLIARY STUDIES:

MASS PROPERTIES ANALYSIS and CONTROL: Accounting, Uncertainty, Standard Deviation and Confidence Level. Estimation of Automotive Mass Properties: Total Weight with Center of Gravity & Inertias; Sprung and Unsprung Weight with Center of Gravity & Inertias; Sprung Weight Roll Moment of Inertia. Products of Inertia: Reference Axes System Transformation - Design Axes System to Principal Axes System and to Roll Axes System. Static and Dynamic Balance.

TIRE BEHAVIOR: Traction Ellipse, Vertical Spring Rate, Contact Area, Tread Width, Deflection Under Load, Slip Percent, Slip Angle, Hydroplaning, Standing Wave, Load Capacity, Rolling Resistance, Wear.

AERODYNAMICS: Frontal Area, Plan Area, Drag (Form, Skin), Lift.


AUTOMOTIVE DYNAMICS, ADVANCED TOPICS: SUSPENSION GEOMETRY: Background History -

Attenuation of Road Shock and Vibration. Suspension Types & Characteristics: Camber, Castor, Scrub, Roll Center, Unsprung Mass.

STEERING GEOMETRY: Background History - Evolution of Steering: Erasmus Darwin, Georg Lankensperger, Rudolf Ackermann, Charles Jeantaud. Steering Geometry and Equations.

GYROSCOPIC REACTIONS: Reaction to Precession with Camber & Steer. Magnitude of Reaction: The Equation. Direction of Reaction: The Right Hand Rule.

FUEL ECONOMY: Sources of Energy Loss, Effect of Weight / Inertia and Aero Drag / Lift. Fuel Consumption, City / Highway and Combined.


AUTOMOTIVE DESIGN, MAIN ASPECTS OF STYLING:FUNCTIONTHEMEFORMPROPORTIONLINERHYTHMCOLORCONTRASTTEXTURE


AUTOMOTIVE DESIGN, BASIC STYLING PHILOSOPHY:

STYLING MUST BEGIN WITH A “DRAWING BY HAND”; THERE IS A COORDINATION BETWEEN THE HUMAN HAND AND EYE THAT MUST BE UTILIZED IF THE GOAL IS TO PRODUCE SOMETHING BEAUTIFUL, WITH “SOUL”.

STYLING MAY BE TOTALLY DONE BY COMPUTER GRAPHICS IF THE GOAL IS TO PRODUCE SOMETHING MERELY SELLABLE, A “SOULLESS” PRODUCT. OFTEN THE STYLIST SETTLES ON SIMPLY BEING DIFFEЯenT, NOT BEAUTIFUL.

AUTOMOTIVE DYNAMICS and DESIGN: SYLLABUS

AUTOMOTIVE DESIGN, STYLING DETAILS: Automotive Styling, Unlike Pure Art Forms, Is a Blend of Art and Engineering; It Is

Constrained by Practical Considerations: Entry and Exit, Access to Engine and Trunk, Etc. Outward Visibility for Driver and Passengers. Legal and Practical Requirements for Bumpers,

Lights, License Plates, Crash Protection. Location and Size of Wheels, Engine,

Passengers. Aerodynamic Considerations: Lift and Drag,

Cooling, Ventilation, Intakes, Exhausts.18


AUTOMOTIVE DESIGN, STYLING DETAILS:

Requires Understanding of:▪ Function, Theme, Form, Proportion, Line, Rhythm,

Color, Contrast, and Texture.▪ Orthographic Projection: Side View, Front View, Rear

View, Plan View.▪ 3-D Perspective: One Point, Two Point, Ellipses.▪ Rendering: Light and Shadow, Reflection.

Styling Process:▪ Old School: Drawing, Clay, Prototype, Testing,

Refinement, Production.▪ Modern School: Drawing, Computer, CNC Machining /

3-D Printing, Prototype, Testing, Refinement, Production.

19


AUTOMOTIVE DESIGN, 1964 STYLING EXAMPLE:

20



21



21



22



23



24



25



26


AUTOMOTIVE DESIGN, 1964 STYLING STUDIO:

27


AUTOMOTIVE DYNAMICS and DESIGN

END of SYLLABUS

28


AUTOMOTIVE DYNAMICS and DESIGN, INSTRUCTOR’S CREDENTIALS:

GRADUATE FARMINGDALE SHS, NY, 1967. GRADUATE PRATT INSTITUTE, NY, BME, 1972. PROFESSIONAL ENGINEER LICENSE, NY, 1981. SAE SEMINAR “VEHICLE DYNAMICS for PASSENGER

CARS and LIGHT TRUCKS”, 2009. 37+ YEARS INDUSTRY EXPERIENCE. MEMBER SAWE, SAE. FORMER MEMBER ASME, SNAME,

ASNE. 2 INDUSTRIAL AWARDS, 5 SOCIETY AWARDS. 24 TECHNICAL PAPERS / JOURNAL ARTICLES.

29

Brian Paul Wiegand, B.M.E., P.E.: