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, flight dynamics, 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
Suspension and steering
Some attributes relate to the
geometry of the suspension,
steering and
Rolling chassis. These include:
Distribution of mass
Some attributes or aspects of vehicle dynamics are purely due to
mass and its distribution. These include:
Aerodynamics
Some attributes or aspects of vehicle dynamics are purely
Aerodynamics. These include:
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Automobile drag coefficient
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Automotive aerodynamics
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Center of pressure
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Downforce
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Ground effect in cars
Tires
Some attributes or aspects of vehicle dynamics can be attributed directly to the
. These include:
Vehicle behaviours
Some attributes or aspects of vehicle dynamics are purely dynamic. These include:
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 package such as
MSC Software 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.[Rachel Evans Quantum leaps , Automotive Testing Technology International, September 2015, p.43 quote from MTS' Mark Gillian: " From an OEM perspective, thermal modelling may be overkill but the tire models are still the weak point of any vehicle model"] 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.
Sim racing 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:
See also
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Automotive suspension design
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Automobile handling
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Hunting oscillation
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Multi-axis shaker table
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Vehicular metrics
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4-poster
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7 post shaker
Further reading
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A new way of representing tyre data obtained from measurements in pure cornering and pure braking conditions.
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Mathematically oriented derivation of standard vehicle dynamics equations, and definitions of standard terms.
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Vehicle dynamics as developed by Maurice Olley from the 1930s onwards. First comprehensive analytical synthesis of vehicle dynamics.
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Latest and greatest, also the standard reference for automotive suspension engineers.
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Vehicle dynamics and chassis design from a race car perspective.
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Handling, Braking, and Ride of Road and Race Cars.
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Lecture Notes to the MOOC Vehicle Dynamics of iversity
