01_IntroOverview_pptx

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ME 360/390 Prof. R.G. LongoriaVehicle System Dynamics and Control

Department of Mechanical EngineeringThe University of Texas at Austin

Vehicle System Dynamics and ControlIntroduction and Course Overview

Prof. R.G. Longoria

Spring 2013


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Overview

These slides were not presented in lecture.

The content reviews some ideas and conceptsthat have motivated this course and the

contents.

Review at a high level.

Any comments are appreciated.


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A definition of mobility

mobile adj. capable of moving or being moved

mobility n. having the capacity to move or to bemoved from place to place

locomotion n. the act of moving or ability to

move from place to place (L locus, place)

This course is concerned with how vehicle systems and

controls enable locomotion via ground mobility.


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Vehicle Systems

In our current technological state, enhanced

mobility requires use of a vehicle.

Vehicle n. Any device for carrying passengers,

goods, or equipment, usually one moving on

wheels or runners, as a car or sled. Automotive adj. of or pertaining to self-

propelled vehicles


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Automotive On-Road, Passenger

GM Autonomy concept

BMW Series 7 roll stabilization

Prius

SaturnEscapeF-150

Continuous

technology

innovation


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Off-Road Industrial/Utility/Military

Toro Dingo


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ME 360/390 Prof. R.G. LongoriaVehicle System Dynamics and Control Department of Mechanical EngineeringThe University of Texas at Austin

Unmanned/Robotic GVs

Foster-Miller TALON

iRobot PackBot

NASA Spirit

Crusher

(CMU)

Urban Challenge (Stanford, VaTech)

Google


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Personal Mobility

Powered wheel-chairs

SegwayHuman

Transporter

Human/NaturePowered Wheels

Bicycles

chainless

Too innovative?


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GV Classifications

On-road, passenger

Off-road, industrial, military

Unmanned, autonomous

Personal mobility

Discussion Problem 1: These types of classifications imply

certain types of constraints on the overall vehicle design based

on how it is expected to operate.

Choose the application area that interests you and discuss some of

the design requirements that you think would be important.


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Ground Vehicle Classification

Ground vehicle n. vehicles that are supported by the

ground, in contrast to aircraft and marinecraft that in

operation are supported by air and water, respectively

Guided Ground Vehicle n. constrained to move along

a fixed path (guide-way), such as railway vehicles and

tracked levitated vehicles

Non-Guided Ground Vehicle n. can move in various

directions on the ground, such as on-road and off-road

vehicles.

Ref.: J.Y. Wong, Theory of Ground Vehicles


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Motion of a non-guided ground vehicle is

controlled almost entirely by forces developed

between the running gear (tires, tracks, or runners)

and the road or terrain.

These forces need to be well understood!

Only for brief moments might

this not be true.

CarSim simulation of a vehicle

leaving ground(see clog for link to animation).


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Morphology of Motor Vehicles and Environment

per BekkerBekker (1956) discusses the following concepts

in vehicle design, providing a basis for

challenging the evolution of vehicle types.

Form index

Specific weight Size and Form

Origin of Forms

Form, environment, and their relationship

Stabilization of Forms and Vehicle Concept

Bekkers seminal works examine

how a vehicle should be designedto meet requirements while

considering the environment.


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Mieczyslaw G. Bekker

(1905-1989)M.G. Bekker was a Polish-American engineer and scientist who

graduated from Warsaw Technical University (Warsaw, Poland) in 1929.

He moved to France in 1939, and from 1942 lived in Canada and the

U.S. before finally settling in the U.S. in 1956.

He was a leading specialist in the theory and design of military and off-the-road

locomotion vehicles, and an originator of a new engineering discipline called

"terramechanics". He worked for Polish Ministry of Military Affairs (1931-1939), lectured

at the Warsaw Technical University (1936-1939) and several U.S. universities, then

worked in General Motors laboratories in Santa Barbara, CA (1960-1970), and consulted

with the Canadian and U.S. armies.

Bekker authored the general idea and contributed significantly to the design and

construction of the LRV (Lunar Roving Vehicle) used by missions Apollo 15, Apollo 16,

and Apollo 17 on the Moon. He was an author of several patented inventions in the area of

off-the-road vehicles, including those for extraterrestrial use.


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Form and EnvironmentIf the impact of the environment

upon a vehicle form can be

reflected in the value of the

operational speed, then theattempt to improve vehicle

morphology could be reduced to

the study of means which would

increase that speed in various

terrain conditions, as visualized by

the combination of various

degrees of surface roughness withvarious degrees of mechanical

strength of soil.

(Bekker, 1956, p. 89)


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Bekkers work addressed selection of

appropriate vehicle design for a givenenvironment

I like these conceptual sketches!


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Course Objectives

Study basic vehicle dynamics and gain familiarity with concepts

in performance, handling, and ride analysis

Practice using system analysis and design tools with the intentof increasing our capacity to

understand and design modern and future vehicle systems/subsystems,

understand these systems well enough to provide design support and

diagnostic input, understand the impact of system changes on the practical aspects of

manufacturing either production vehicles or one-off prototype vehicles.

Use analytical/computational tools useful in vehicle system

analysis and control design

Study specific vehicle designs in typical operations on terrains

of interest


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Type of background expected An engineering background with good knowledge of mechanics

Prepared and willing to study and apply concepts from dynamic systems, vibrations,

and control systems, and the typical type of mathematical models used in these areas:

ODEs, state space, transfer functions, etc.

Know how to run a digital simulation and how to present results and be willing to

spend time getting these types of solutions running correctly

Willing to learn how to use new types of software for modeling and analysis:

Matlab/Simulink, LabVIEW Control and Simulation, MSC.ADAMS

This course is meant to provide an opportunity to learn about vehicle dynamics and

vehicle control systems. Active participation in the process is expected, including

exploring other references and finding resources that improve understanding and

expand on what has been discussed during lecture.

It is not possible to cover everything during lecture that might be needed to solve all

homework or project work, and it is expected that you will fill in gaps as needed to

improve your understanding.


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ME 379M/397 Prof. R.G. LongoriaVehicle System Dynamics and Control Department of Mechanical EngineeringThe University of Texas at Austin

Driver-Vehicle-Ground System

Visual andOther Inputs

Ground Conditions

Driver

Accelerator,

Brakes

Steering

System

SurfaceIrregularities

Aerodynamic Loads

Performance

Handling

Ride

Adapted from Wong (2001)

From Doebelin (1980)

System-level diagram

Vehicle systems and principal

types of operating modes


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Remaining Discussion

Assessing ground vehicle design

Overview of vehicle system dynamics and

types of models

Control systems in vehicles


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Assessing Ground Vehicle Design

How can you make sure that the (electro-mechanical) design of a vehicle enables it to be

controlled to achieve specified mobilityrequirements?

How do you rationalize a design?

Rational mechanics (a definition):http://science.jrank.org/pages/10483/Newtonianism-Rational-Mechanics.html

NOTE: I consider Wongs book takes more of a rational mechanics view, asopposed to Gillespies book which I think has a strong design appeal.


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Models for Design/ControlOur goal (in this course) is to study and gain appreciation for models

appropriate for a given vehicle application/analysis:

Large-scale, nonlinear complex, highly detailed computer models

Very complex, subsystem models

Require high maintenance and complex assembly

Extensive development time (2-6 man/months), extensive data collection forparameters

Capable of very impressive animations (CarSim, TruckSim, ADAMS, etc.)

Small scale, linear or nonlinear models Mostly differential equations, combined with look-up tables, data, etc.

Use steady state simplification or as computer models

Used for the design and analysis of vehicle dynamics, embedded computercontrols

Fast computational time Low cost to run and relatively short development time

Useful for running many parametric studies


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Choosing a ModelMajor deciding factors are cost and time. The more detailed the

model the higher the cost in terms of computer hardware,

development time, run time and delivery time. It is always

advisable to attempt to create a model that:

1. Has only as many states as needed to capture the dominant modes of behavior that

we are interested in.

2. Has the least number of parameters; each parameter is associated with a datacollection cost and minimizing the data will minimize the total cost of the model.

Furthermore, vehicle data is usually stochastic: the car mass is not fixed, it

changes with the number of passengers or the amount of fuel in the tank, so does

the tire stiffness that changes depending on the tire temperature. The smaller themodel the less data is required and that reduces uncertainty error in the model.


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Dynamics and System Dynamics

Basic force analysis

Skid steer (Bekker)

Steering and handling

Traction/BrakingThese figures illustrate

typical analysis/modeling

required vehicle systemdynamics.

Emphasis on:

-simplifying the model

-using basic analysis that

includes use of proper

coordinate systems, FBDs,

force analysis, etc.


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Vehicle Drive Train Systems

Gillespie (1992)

Drive trains are formed from:

Clutches

Manual transmissions and transaxles

Automatic transmissions Electric drives

Karnopp and Rosenberg (1970)


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Vehicle Performance

We are here concerned with evaluating a vehicles ability to:

Accelerate

Develop drawbar pull Overcome obstacles

Decelerate

For a given application, it is necessary to decide

how detailed to model the powertrain, tire-road

interaction, etc.

Purpose:

For insight on how to improve the

acceleration and braking responses of the

vehicle.

To determine the engine and powertraincharacteristics

Assess energy consumption, efficiency, etc.


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Power-Speed Limits for Vehicles

This graph shows estimates of

maximum attainable speed for given

vehicle specific power.

The lower the line, the moreefficient the mode of locomotion.

Gabrielli and von Karman found

main factor is mechanical properties

of materials (see clog for paper). Radical improvements may need

to look at other than material

improvements.

Resistance of the environment tolocomotion also a large factor.

Bekker, 1960

Wheels on rails have a

very different ratio of

frontal area to mass andfall below the G-vonK line

(much lower aero losses)

[ ]

20.001 hp/ton

mph

Pv

mg

v

=

=

We may revisit this basic measure later

when we study performance modeling.


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Vehicle Steering and Handling

Qualities that refer to the response of the vehicle to the drivers commands

and its ability to stabilize its motion against external disturbances.

Handling evaluates the dynamics of the vehicle in response to driver's

steering input. It includes cornering, directional stability, roll-over, and loadtransfer.

With a driver in the loop, the vehicle system is considered closed-loop.

Vehicle characteristics are often developed with specific steering inputs, for

example, in order to derive open-loop response.

Purpose:

To improve the ability of the car to follow a desired steering input curve.

Steering and suspension mechanisms rely on results from handling analysis.


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Handling

Concerned with the motions of acar outside of its plane ofsymmetry

responsiveness of a vehicle todriver input or the ease ofcontrol

Handling often refers to anoverall measure of vehicle-driver interaction

ease by which it is possible to steer orachieve a desired path

ease by which a path or heading ismaintained

Segel (1956)

Handling is concerned with the

yawing, rolling, and sideslipping

as might result from steeringinputs or disturbances (e.g., wind,

road, etc.)


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ME 360/390 Prof. R.G. Longoria

Vehicle System Dynamics and Control Department of Mechanical EngineeringThe University of Texas at Austin

Example: Selecting Handling Model

Select or develop a model with yaw and lateralvelocity as state variables.

This basic and relatively low cost model isuseful for dynamic as well as steady stateturning, and can be used to experiment withfeedback controls for vehicle steering.

Once a design is completed it can then be tested on more detailed and larger scale

computer models that include significant nonlinearities and more states.

The large scale models are less costly than testing on real cars, and allow for

repeatable testing.Testing a physical vehicle might follow testing and parametric study using the

computer simulations, which might be first used to fine tune a design.


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Vehicle Ride

Ride characteristics are related to the vibration of the vehicleexcited by surface irregularities and its effect on passengersand/or payload.

Ride can specifically refer to tactile and visual vibration (0-25Hz), while aural vibrations are characterized as noise (25-20,000 Hz).

Purpose:

To evaluate vehicle vibration, a critical criteria for judging thequality of a vehicle.

To improve comfort and road isolation while maintainingwheel/ground contact.

Suspension system design is primarily based on ride analysis.


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Vehicle Vibration Models

Level of difficulty


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Example: CarSim model

Body-fixed coordinate axes

5 rigid bodies (body, 4 wheels)

Vehicle body with 6 degrees of freedom (DOF)

4 wheels have 1 translational DOF relative tothe body

Each wheel has force from suspension

tire force (3 directional components)

Spin of wheels can be included in drivetrain

separately from vehicle body/wheel dynamics

See the Carsim website: www.carsim.com

We may use an educational version of this program.


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Stability and Control

Stability and control concepts will be

introduced to study how a baseline vehicle

system may perform.

In addition to application to typical on-road

vehicles, we may examine other types ofsystems such as:

Ground robotic vehicles

Personal mobility vehicles (bicycles, skateboards,etc.)


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Vehicle Control Systems

Modern ground vehicle systems take advantage of and havemotivated many advancements in sensor, actuator, andcomputing technologies to achieve and/or improve

performance in many different ways. Vehicle control systems can be categorized into three areas:

Powertrain control this involves control of the power plant (e.g.,engine) and power transmission systems

Vehicle motion control refers to control of a vehicles motion, andincludes ground speed control (cruise), braking/traction control,suspension control, and steering control

Body control refers to systems that enhance energy control,communications, comfort, etc.

In this course, we are mostly concerned with vehicle motion andto a lesser extent with powertrain; these two are somewhatintegrated in modern systems.


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Vehicle Dynamics Control (VDC)

To enhance vehicle dynamic response, steering,

stability, ride and handling

Suspension control

Steering control

Braking control (e.g., ABS) Traction control systems (TCS)

Electronic stability program (ESP) Electronic transmission-shift control


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Vehicle Subsystems Control

Engine management and control

Driveline control

Electrical/electronic systems

starter systems

instrumentation and lighting

comfort (cruise control, temperature, etc)

Occupant safety systems

restraint

rollover

Body

control

Powertrain

control


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Vehicle InnovationsDeveloped in Stages

Basic: anti-lock braking,

traction control*

Next-stage: interactive

vehicle dynamics (IVD)

control or vehicle stabilitycontrol (VSC)

Trend is toward coordinated

efforts to achieve objectives

*adapts engine torque to match available traction

Powers and Nicastri (2000)


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Vehicle System Dynamics and ControlDepartment of Mechanical Engineering

The University of Texas at Austin

Reliance on

SensingSensors form an integral part of

modern vehicles.

Information from the sensors

must be shared, and significant

effort is required to make thiscost effective.

Powers and Nicastri (2000)


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Electronic Stability Program (ESP)

Without ESP

With ESP

From Bosch, 1999


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Summary

We cant do it all remind me of that (when I go on tangents)

Review dynamics as we introduce the different types of vehicle

models. Motivate the need for controls.

Use computer-based analysis and simulation to understand

response behavior and the influence of controllers.

There is some baseline material that will be covered through

assignments/homework, with extensions made through projects.

Have fun, build an appetite to learn more in this field.

New for 2013: incorporate a writing project


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References

Bekker, M.G., Theory of Land Locomotion: The Mechanics of Vehicle Mobility, The

University of Michigan Press, Ann Arbor, MI, 1956 (1962).

Bosch, R., Driving Safety Systems, SAE, 1999.

Doebelin, E.O., System Modeling and Response, John Wiley and Sons, New York, 1980.

Gillespie, T.D., Fundamentals of Vehicle Dynamics, SAE, Warrendale, PA, 1992.

Goodwin, G.C., S.F. Graebe, and M.E. Salgado, Control System Design, Prentice-Hall, 2001.

Hrovat, D. and W.F. Powers, Computer Control Systems for Automotive Power Trains, IEEE

Control Systems Magazine, Vol. 8, pp. 3-10, August 1988.

Karnopp, D. and R. Rosenberg, Application of Bond Graph Techniques to the Study of Drive

Line Dynamics, Journal of Basic Engineering (ASME), pp. 355-362, June 1970.

Powers, W.F. and P.R. Nicastri, Automotive vehicle control challenges in the 21st century,

Control Engineering Practice, Vol. 8, pp. 605-618, 2000.

Rajamani, R., Vehicle Dynamics and Control, Springer, New York, 2006.

Ribbens, W.B., Understanding Automotive Electronics, Newnes, 1998 (5th edition). (1982

edition, Radio Shack)

Stockel, M.W., M.T. Stockel, and C. Johanson, Auto Fundamentals, The Goodheart-Willcox

Company, Inc., Tinley Park, IL, 1996.

N


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Notes

Classical vehicle system dynamics assumes the body to be a rigid mass with

six degrees of freedom.

These degrees of freedom are studied separately under the assumption that

for certain conditions only a subset of these six degrees of freedom willrepresent the dominant motion of the vehicle.

Longitudinal acceleration and braking are studied separately usually under

the title road loads.

Lateral motion and yaw, the name given to the angular motion in thehorizontal plane, are studied in "handling".

Heave and pitch, the names given to the vertical motion and the angular

motion in the vertical plane, are usually separated and studied as "ride".

N ( )


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Notes (cont)

Ground vehicle design is an increasingly complex multi-disciplinary

engineering task.

We need to understand how forces and moments are related to the position,

velocity, and acceleration of a ground vehicle. These forces and momentsmay:

result from the surrounding environment, through the tires or body, thus the

importance of road roughness and air drag, or

be internally generated by vehicle subsystems, such as the engine, powertrain, or

suspension mechanisms.

Classical vehicle dynamics uses steady-state analysis which provides

adequate design equations, relying on minimal complexity in models of tires

and of the tire/road interface, dynamics of ride, steady state traction, and

steady state steering.

The arrival of digital computers has made more detailed and comprehensive

analysis possible.

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Notes (cont)

Other important topics can be encountered in the study of vehicle dynamics,

including tire dynamics, engine and powertrain dynamics.

Tire dynamics is a field of critical importance in vehicle performance. The

study of tire dynamics in the scope of vehicle dynamics attempts atdeveloping mathematical and computer models that predict the dynamics of

the pneumatic tire.

The analysis of powertrain dynamics including the dynamics of the clutch,

transmission system, and final drive, includes the interaction between theengine, powertrain, wheel, tire, and terrain with the objective of improving

the longitudinal time response of the vehicle.

The challenge that faces vehicle system dynamicists today is not only in

merely understanding the complex nonlinear dynamics of these areas but

also in using modern CAD/CAE/CAM tools to integrate their design and

computer controls in order to produce a highly responsive, comfortable, and

safe ground vehicle.

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