Vehicle dynamics

Vehicle dynamics is the study of vehicle motion, e.g., how a vehicle's forward movement changes in response to driver inputs, propulsion system outputs, ambient conditions, air/surface/water conditions, etc.
Vehicle dynamics is a part of engineering primarily based on classical mechanics.
It may be applied for motorized vehicles (such as automobiles), bicycles and motorcycles, aircraft, and watercraft.
Factors affecting vehicle dynamics
The aspects of a vehicle's design which affect the dynamics can be grouped into drivetrain and braking, suspension and steering, distribution of mass, aerodynamics and tires.
Drivetrain and braking
Automobile layout (i.e. location of engine and driven wheels)
Powertrain
Braking system
Suspension and steering
Some attributes relate to the geometry of the suspension, steering and chassis. These include:
Ackermann steering geometry
Axle track
Camber angle
Caster angle
Ride height
Roll center
Scrub radius
Steering ratio
Toe
Wheel alignment
Wheelbase
Distribution of mass
Some attributes or aspects of vehicle dynamics are purely due to mass and its distribution. These include:
Center of mass
Moment of inertia
Roll moment
Sprung mass
Unsprung mass
Weight distribution
Aerodynamics
Some attributes or aspects of vehicle dynamics are purely aerodynamic. These include:
Automobile drag coefficient
Automotive aerodynamics
Center of pressure
Downforce
Ground effect in cars
Tires
Some attributes or aspects of vehicle dynamics can be attributed directly to the tires. These include:
Camber thrust
Circle of forces
Contact patch
Cornering force
Ground pressure
Pacejka's Magic Formula
Pneumatic trail
Radial Force Variation
Relaxation length
Rolling resistance
Self aligning torque
Skid
Slip angle
Slip (vehicle dynamics)
Spinout
Steering ratio
Tire load sensitivity
Vehicle behaviours
Some attributes or aspects of vehicle dynamics are purely dynamic. These include:
Body flex
Body roll
Bump Steer
Bundorf analysis
Directional stability
Critical speed
Noise, vibration, and harshness
Pitch
Ride quality
Roll
Speed wobble
Understeer, oversteer, lift-off oversteer, and fishtailing
Weight transfer and load transfer
Yaw
Analysis and simulation
The dynamic behavior of vehicles can be analysed in several different ways. This can be as straightforward as a simple spring mass system, through a three-degree of freedom (DoF) bicycle model, to a large degree of complexity using a multibody system simulation package such as MSC ADAMS or Modelica. As computers have gotten faster, and software user interfaces have improved, commercial packages such as CarSim have become widely used in industry for rapidly evaluating hundreds of test conditions much faster than real time. Vehicle models are often simulated with advanced controller designs provided as software in the loop (SIL) with controller design software such as Simulink, or with physical hardware in the loop (HIL).
Vehicle motions are largely due to the shear forces generated between the tires and road, and therefore the tire model is an essential part of the math model. In current vehicle simulator models, the tire model is the weakest and most difficult part to simulate. The tire model must produce realistic shear forces during braking, acceleration, cornering, and combinations, on a range of surface conditions. Many models are in use. Most are semi-empirical, such as the Pacejka Magic Formula model.
Racing car games or simulators are also a form of vehicle dynamics simulation. In early versions many simplifications were necessary in order to get real-time performance with reasonable graphics. However, improvements in computer speed have combined with interest in realistic physics, leading to driving simulators that are used for vehicle engineering using detailed models such as CarSim.
It is important that the models should agree with real world test results, hence many of the following tests are correlated against results from instrumented test vehicles.
Techniques include:
Linear range constant radius understeer
Fishhook
Frequency response
Lane change
Moose test
Sinusoidal steering
Skidpad
Swept path analysis
See also
Automotive suspension design
Automobile handling
Hunting oscillation
Multi-axis shaker table
Vehicular metrics
4-poster
7 post shaker
References
Further reading
A new way of representing tyre data obtained from measurements in pure cornering and pure braking conditions.
Mathematically oriented derivation of standard vehicle dynamics equations, and definitions of standard terms.
Vehicle dynamics as developed by Maurice Olley from the 1930s onwards. First comprehensive analytical synthesis of vehicle dynamics.
Latest and greatest, also the standard reference for automotive suspension engineers.
Vehicle dynamics and chassis design from a race car perspective.
Handling, Braking, and Ride of Road and Race Cars.
Lecture Notes to the MOOC Vehicle Dynamics of iversity
Automotive engineering
Automotive technologies
Driving techniques
Dynamics (mechanics)
Vehicle technology