Vehicle Dynamics & Safety

Vehicle Dynamics & Safety

Prof. Vittorio Lorenzi (UniBG) &Prof. Mike Blundell (Coventry-UK)


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 (5-

6-7 of June)


Prerequisites come from Ingegneria dei Sistemi Meccanici: :

• point dynamics• planar kinematics/dynamics of rigid bodies

and mechanisms • dynamics of machines• 1 dof vibrations


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


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 ImpactCourse of Mechanical & Automotive EngineeringFACULTY OF ENGINEERING AND COMPUTINGMain Duties: Head of Vehicle Dynamics and Safety Applied Research GroupQualifications 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 PolytechnicResearch 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 profileMethods: 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)


Four post three axis full scale physical test


Ride influenced by suspension characteristics: mass, stiffness, damping, kinematics. Left McPherson, right rigid axle


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.)


Typical use of bicycle model: linear state equation relating yaw and lateral speed with steering angle, lateral speed after a step steering


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 anti-lock 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 630-880 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.


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):

• Handling and Ride• ABS, ESP, ASR, EBD• Acoustic signal• Lighting• Field of vision (mirrors,

wipers, windshield)

• Tyre condition

• Passive safety (Mitigation of injuries):

• Car Body crashwortiness (front, side, rear collision; rollover)

• Restraint system (seat belts, airbags)

• Vehicle compatibility• Pedestrian protection

Crashwortiness / occupant protection

Syllabus• 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.


• 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

• 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

• Milliken, William F. Race car vehicle dynamics / William F. Milliken, Douglas L. Milliken 1995

• Ellis, John Ronaine Vehicle handling dynamics / by John R. Ellis 1994

• Gillespie, Thomas D. Fundamentals of vehicle dynamics / Thomas D. Gillespie

Documents

Vehicle Dynamics & Safety