Quattro (four-wheel-drive system)Quattro (meaning four in Italian and stylized in lower case) is the trademark used by the automotive brand Audi to indicate that all-wheel drive (AWD) technologies or systems are used on specific models of its automobiles. The word "quattro" is a registered trademark of Audi AG, a subsidiary of the German automotive concern, Volkswagen Group. Quattro was first introduced in 1980 on the permanent four-wheel drive Audi Quattro model, often referred to as the Ur-Quattro (meaning "original" or "first").
Four-wheel driveFour-wheel drive, also called 4×4 ("four by four") or 4WD, refers to a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case providing an additional output drive shaft and, in many instances, additional gear ranges. A four-wheel drive vehicle with torque supplied to both axles is described as "all-wheel drive" (AWD).
BrakeA brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Most brakes commonly use friction between two surfaces pressed together to convert the kinetic energy of the moving object into heat, though other methods of energy conversion may be employed. For example, regenerative braking converts much of the energy to electrical energy, which may be stored for later use.
Electromagnetic brakeElectromagnetic brakes or EM brakes are used to slow or stop vehicles using electromagnetic force to apply mechanical resistance (friction). They were originally called electro-mechanical brakes but over the years the name changed to "electromagnetic brakes", referring to their actuation method which is generally unrelated to modern electro-mechanical brakes. Since becoming popular in the mid-20th century, especially in trains and trams, the variety of applications and brake designs has increased dramatically, but the basic operation remains the same.
Eddy current brakeAn eddy current brake, also known as an induction brake, Faraday brake, electric brake or electric retarder, is a device used to slow or stop a moving object by generating eddy currents and thus dissipating its kinetic energy as heat. Unlike friction brakes, where the drag force that stops the moving object is provided by friction between two surfaces pressed together, the drag force in an eddy current brake is an electromagnetic force between a magnet and a nearby conductive object in relative motion, due to eddy currents induced in the conductor through electromagnetic induction.
Front-wheel driveFront-wheel drive (FWD) is a form of engine and transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitudinal engine arrangement generally found in rear-wheel drive and four-wheel drive vehicles. Car layout#Front-wheel-drive layouts By far the most common layout for a front-wheel drive car is with the engine and transmission at the front of the car, mounted transversely.
Brake-by-wireBrake-by-wire technology in the automotive industry is the ability to control brakes through electronic means, without a mechanical connection that transfers force to the physical braking system from a driver input apparatus such as a pedal or lever. The three main types of brake-by-wire systems are: electronic parking brakes which have, since the turn of the 21st century, become more common; electro-hydraulic brakes (EHB) which can be implemented alongside legacy hydraulic brakes and as of 2020 have found small-scale usage in the automotive industry; and electro-mechanical brakes (EMB) that use no hydraulic fluid, which as of 2020 have yet to be successfully introduced in production vehicles.
Drum brakeA drum brake is a brake that uses friction caused by a set of shoes or pads that press outward against a rotating cylinder-shaped part called a brake drum. The term drum brake usually means a brake in which shoes press on the inner surface of the drum. When shoes press on the outside of the drum, it is usually called a clasp brake. Where the drum is pinched between two shoes, similar to a conventional disc brake, it is sometimes called a pinch drum brake, though such brakes are relatively rare.
Anti-lock braking systemAn anti-lock braking system (ABS) is a safety anti-skid braking system used on aircraft and on land vehicles, such as cars, motorcycles, trucks, and buses. ABS operates by preventing the wheels from locking up during braking, thereby maintaining tractive contact with the road surface and allowing the driver to maintain more control over the vehicle. ABS is an automated system that uses the principles of threshold braking and cadence braking, techniques which were once practiced by skillful drivers before ABS was widespread.
Epicyclic gearingAn epicyclic gear train (also known as a planetary gearset) consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates the planet and sun gears mesh so that their pitch circles roll without slip. A point on the pitch circle of the planet gear traces an epicycloid curve. In this simplified case, the sun gear is fixed and the planetary gear(s) roll around the sun gear.
Transmission (mechanical device)A transmission (also called a gearbox) is a mechanical device which uses gears to change the speed or direction of rotation in a machine. Many transmissions have multiple gear ratios, but there are also transmissions that use a single fixed gear ratio. Most currently-produced passenger cars with petrol or diesel engines use transmissions with 5-8 forward gear ratios and one reverse gear ratio. Electric vehicles typically use a single-speed or two-speed transmission.
Semi-automatic transmissionA semi-automatic transmission is a multiple-speed transmission where part of its operation is automated (typically the actuation of the clutch), but the driver's input is still required to launch the vehicle from a standstill and to manually change gears. Semi-automatic transmissions were almost exclusively used in motorcycles and are based on conventional manual transmissions or sequential manual transmissions, but use an automatic clutch system.
TorqueIn physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). It describes the rate of change of angular momentum that would be imparted to an isolated body. The concept originated with the studies by Archimedes of the usage of levers, which is reflected in his famous quote: "Give me a lever and a place to stand and I will move the Earth". Just as a linear force is a push or a pull applied to a body, a torque can be thought of as a twist applied to an object with respect to a chosen point.
PrecessionPrecession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called nutation. In physics, there are two types of precession: torque-free and torque-induced.
