Vehicle Dynamics & Safety
Prof. Vittorio Lorenzi (UniBG) &
Prof. Mike Blundell (Coventry-UK)
Vehicle Dynamics & Safety
Lessons timetable
• -Monday 11.30-13.30
• -Thursday 10.30-13.30 (12.30)
• -3/4 sessions in computer lab (Matlab/Adams)
• -15 hours with prof. Blundell in three days (56-7 of June)
Vehicle Dynamics & Safety
Prerequisites come from Ingegneria dei Sistemi
Meccanici: :
• point dynamics
• planar kinematics/dynamics of rigid bodies
and mechanisms
• dynamics of machines
• 1 dof vibrations
Vehicle Dynamics & Safety
Final assessment: oral examination
• 1 subject one’s choice
• 2 (?) “free” questions
• Free use of course slides … and formulas
• “Free” choice of dates during sessions ( better
small groups of 3-4 students), contact
[email protected]
• Materials (and announcements):
http://mech.unibg.it
Vehicle Dynamics &Safety
Vehicle Dynamics & Safety
Prof. Mike Blundell
• http://wwwm.coventry.ac.uk
• www. youtube.com: Computer Simulation in Vehicle
Dynamics - Professor Mike Blundell
Prof. Blundell position & research
Professor of Vehicle Dynamics and Impact
Course of Mechanical & Automotive Engineering
FACULTY OF ENGINEERING AND COMPUTING
Main Duties: Head of Vehicle Dynamics and Safety Applied Research
Group
Qualifications
1997, Ph.D., The Influence of Suspension and Tyre Modelling on Vehicle
Handling Simulation, Coventry University
1982, M.Sc., Naval Architecture, University College London
1979, B.Sc , Civil Engineering, Plymouth Polytechnic
Research Interests
Vehicle Handling and Braking Computer Simulation
Pedestrian Impact Protection
Vehicle Crash Analysis
Tyre Modelling and Behaviour
Helicopter Crash Simulation
Prof. Mike Blundell
Vehicle Dynamics
• Vehicle dynamics focuses on these three main
aspects:
• Ride
• Handling
• Longitudinal dynamics
Vehicle Dynamics: Ride
Ride: vertical dynamics or behaviour on ondulating road profile
Methods: multibody systems dynamics (left) with hundreds of d.o.f.
and nonlinearities and/or vibration analysis (right) with few d.o.f. (i.e.
4)
Vehicle Dynamics: Ride
Four post three axis full scale physical test
Vehicle Dynamics: Ride
Ride influenced by suspension characteristics: mass, stiffness,
damping, kinematics. Left McPherson, right rigid axle
Vehicle Dynamics: Ride
Quality of ride must be evaluated in relation to application
(sport/army or standard vehicle) and response of human being
to vibration (tolerance diagram)
Vehicle Dynamics: Handling
Vehicle behaviour on curved path.
Methods: multibody approach with hundreds of d.o.f. and/or
reduced models (i.e. Bicycle model with 3 d.o.f.)
Vehicle Dynamics: Handling
Typical use of bicycle model: linear state equation relating yaw and
lateral speed with steering angle, lateral speed after a step steering
Vehicle Dynamics: Handling
Bosch’s test facility is a complex track comprised of μ surfaces, traction hills,
Vehicle Dynamics Area (VDA) and various other special test surfaces. The antilock brake test track included 2,500 ft. of acceleration and test road. The VDA
features a 21-acre bituminous test pad that is 1,150 ft. long with a width from 630880 ft. A 36 ft. x 4,300 ft. loop road to access the pad was designed with a 1,300
ft. parabolic cross section curve at the west end for testing and acceleration onto
the VDA pad. Ghafari designed the original test track in 1990, as well the VDA
replacement in 2008.
Vehicle Dynamics: Handling
Handling quality can be improved by a control system, based on
vehicle simplified model.
Longitudinal Dynamics
Vehicle behaviour in rectilinear path.
At constant speed: power absorbed, fuel consumption, max speed and max
grade. Load on axles. Effect of torque distribution on axles.
During braking/acceleration: optimal load distribution between axles and…
Longitudinal Dynamics
Time required to reach a given speed, gear shiftng and
choice: 1-2 d.o.f. model.
Longitudinal dynamics
Longitudinal behaviour can be improved by control systems:
ABS for braking and ASR/TCS (anti slip regulation, traction control system) for
acceleration
Longitudinal dynamics
• ASR (Anti Spin
Regulation) or TCS
(Traction Control
System)
Vehicle Safety
• Active Safety (accident
avoidance):
• Passive safety
(Mitigation of injuries):
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• Car Body crashwortiness
(front, side, rear collision;
rollover)
• Restraint system (seat belts,
airbags)
• Vehicle compatibility
• Pedestrian protection
Handling and Ride
ABS, ESP, ASR, EBD
Acoustic signal
Lighting
Field of vision (mirrors,
wipers, windshield)
• Tyre condition
Crashwortiness / occupant
protection
Syllabus
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Pneumatico
-caratterizzazione del pneumatico, modello a spazzola e Magic formulae.
-modelli dinamici
Dinamica longitudinale.
-azioni aerodinamiche
-resistenze al moto, pendenza superabile, velocità massima, scelta dei rapporti di trasmissione, consumi,
differenziali.
-transitorio di avviamento, accelerazione, tempo di avviamento.
-frenatura, ripartizione della frenata e dispositivi anti bloccaggio .
Comportamento direzionale.
-sterzatura cinematica e dinamica
-modello a bicicletta
-stabilità, risposta al colpo di sterzo, .steering pad.
-controllo stabilità
Dinamica verticale
-sospensioni: descrizione tipologia e cenni sull’influenza dei moti sospensivi sul comportamento
direzionale.
-comfort e assorbimento delle vibrazioni.
Sicurezza attiva e passiva
-dispositivi di aiuto alla guida
-biomeccanica dell'urto, simulazione dell'occupante
-crash tests, protezione dell'occupante e dei pedoni.
Vehicle Dynamics & Safety
• Frontal lessons
• Numerical examples in Computer Lab.
• Some didactic material (slides) available at
http://mech.unibg.it/~lorenzi
• Lessons taught by prof. Blundell (first week of
June)
• Oral examination
VD&S textbooks
•
Blundell, Michael The multibody systems approach to vehicle dynamics /
Michael Blundell, Damian Harty /2004
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Reimpell, Jörnsen The automotive chassis : chassis and vehicle overall, wheel
suspensions and types of drive, axle kinematics and elastokinematics, steering,
springing, tyres, construction and calculations advice / 2001
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Milliken, William F. Race car vehicle dynamics / William F. Milliken, Douglas L.
Milliken 1995
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Ellis, John Ronaine Vehicle handling dynamics / by John R. Ellis 1994
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Gillespie, Thomas D. Fundamentals of vehicle dynamics / Thomas D. Gillespie