Dictionary

Angles

The terminology for the position angles of a vehicle are Roll, Pitch, Yaw, respectively around the xyz axes.

Kinematics

"Science in which movements are considered in themselves, (independent of the forces that produce them), as we observe them in solid bodies all around us, and particularly in assemblies called machines", as defined by André-Marie Ampère in 1834 in his "Essai sur la philosophie des sciences", from the Greek "kinema", movement. The Belgian Franz Reuleaux, born in 1829, is the father of modern kinematics.

Decarbonated

First coined in the USA in 2008; applies to vehicles :

that consume little or no fossil carbon (such as oil or gas) but can consume biomass carbon (biofuel),
and/or generate low levels of greenhouse gases (such as CO2).

Uncoupled

Originally used to describe a vibratory mode consisting of the movement of a single mass. By extension, it refers to a device enabling decoupled modes to be obtained, e.g. independent stiffness in pumping, pitching and rolling.

Degree of freedom

DdL, DoF in English, number of independent variables in the mathematical model of a system, giving an idea of the finesse of its description; don't forget, however, the linear (see below) or non-linear nature of these variables.

Demonstrator

A demonstrator is a vehicle with the essential functions targeted by the development, and enabling them to be demonstrated "a minima", without having the definitive components and/or processes, nor the ancillary functions. It's a pragmatic approach aimed at eliminating unknowns and minimizing costs. "Empty arguments with words can in no way compare with a test that will show practical results", said Chinese engineer Ma Jun in 237! Proof-of-concept.

Dynamics

Study of movements subject to forces, including the temporal response to commands or disturbances.

Embedded

The in-vehicle approach to road safety considers the situation from the vehicle, with the road and environment as perceived by the vehicle, here and now. The user's point of view.

Ergonomics

Ability to be used by a human being.

Hybrid

The combination of two different things
In the context of automotive motorization, a combination of two different types of motors, for example Eaton buses with an internal combustion engine and a hydraulic motor.
Unless otherwise specified, includes a combustion engine and at least one electric motor.

See a more detailed explanation here...

Ground connection

A more general term than "suspension", which is too reductive, since it does not include steering and transmission functions, and is impossible to use for vehicles which have no suspension as such (a go-kart, a farm tractor, etc.) but which do have comfort, driveability and roadholding functions. For more information, click here.

Linear

In reality, very few phenomena are linear. A metal specimen gradually deforms with the force applied, then breaks. A suspension gradually sinks with the load, then stops. A tire drifts progressively, then abruptly. On the other hand, linear phenomena, or linear portions of phenomena, are easier to analyze.

A bit like the story of the alcoholic who looks for his keys under a lamppost. "Is that where you lost them?" asks a perceptive passer-by. "No, but here, you can see clearly!"

Mode

In a system with several masses and springs, a particular movement where all the masses move at the same frequency, but not necessarily in the same direction or in phase.

Model

Mathematical representation of a physical system.

Modeling means simplifying, because physical models are often not very simple. Validation is therefore essential (see below). For example, human behavior (decision-making, actions, etc.) is difficult to model, and so it is sometimes useful to surround a real driver in a simulation environment, known as a simulator.

The model can be solved literally, by frequency or by time.

The word "simulation" (see below) is reserved for the temporal response to inputs.

Parameters

A useful neologism to clearly distinguish the "set of numerical values" from the model itself, which consists of its degrees of freedom and equations.

Pendular

Type of chassis-suspension organization where the vehicle leans towards the inside of the bend, like a motorcycle. Opposite of Tabular.

Pragmatism

Applied to technology, this is an anti-dogmatic, result-oriented approach, implicitly acknowledging that we don't know everything, and that we need to experiment.

This method is little appreciated in France, where people tend to know everything. On the other hand, it enabled Mercedes, when preparing the 190 model in the 1980s, to try out all possible types of rear suspension on a simple tubular chassis, and thus to go straight from old-fashioned suspensions to the 5-link kinematics known and used, for example, on 1970s Formula 1 cars, and which has since become the standard for all top-of-the-range vehicles under the name of "multi-link".

This approach, which is highly relevant in the field of automotive R&D, is not necessarily generalizable to other fields, such as politics, religion or philosophy: "It doesn't matter whether the cat is black or white, what counts is that it catches mice", Chinese proverb.

Simulator

A special simulation environment where vehicle dynamics are simulated and a driver is placed in the loop. The aim is to provide the driver with the relevant information (visual, haptic, sound, etc.) and to acquire his or her commands.

Digital simulation

Calculation on a digital computer of the temporal response of a system's state variables and derived data to inputs and/or disturbances, enabling "what-if" and optimization of system parameters (see above).

Hybrid simulation

Simulation where elements of different natures interact, for example a computer simulation program and :

a driver (=simulator),
an electronic calculator (=Hardware-in-the-loop),
an engine test bench, see publication no. 23

Statico-dynamics

Study the steady state of a moving solid.

Acceleration is constant; in the case of longitudinal movement, speed is variable at constant longitudinal acceleration, whereas in the case of lateral dynamics, the bend is stabilized at constant lateral acceleration and speed. In both cases, the stabilized state is calculated, and the time response is rarely performed.

The French terminology is not very happy: the English equivalent is "steady-state" or the Italian "in regime".

Tabular

A type of chassis-suspension organization that induces rolling to the outside of the bend, like an ordinary car. Opposite of Pendular.

Validation

Trap word due to its imprecision

In a vehicle dynamics context, compare a model with real tests using an instrumented vehicle.