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Oversteer
Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Oversteer is what occurs when a car turns (steers) by more than the amount commanded by the driver. Conversely, understeer is what occurs when a car steers less than the amount commanded by the driver. Automotive engineers define understeer and oversteer based on changes in steering angle associated with changes in lateral acceleration over a sequence of steady-state circular turning tests. Car and motorsport enthusiasts often use the terminology more generally in magazines and blogs to describe vehicle response to steering in a variety of maneuvers. Vehicle dynamics terminology Standard terminology used to describe understeer and oversteer are defined by the Society of Automotive Engineers (SAE) in document J670SAE International Surface Vehicle Recommended Practice, "Vehicle Dynamics Terminology", SAE Standard J670, Rev. 2008-01-24 and by the International Organization ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinout (driving)
An automobile skid is an automobile handling condition where one or more tires are slipping relative to the road, and the overall handling of the vehicle has been affected. Subtypes of skid include: * fishtailing, where the vehicle yaws back and forth across the direction of motion. * ''spin'' or ''spinout'' where a vehicle rotates in one direction during the skid. * understeer and oversteer where front or rear wheels lose traction during cornering, causing a vehicle to follow a larger or smaller turning radius. * ''burnout'' where a vehicle slips or spins its tires during acceleration. * skidding during braking (with or without directional or yaw changes). __TOC__ Slip and skid Tire slip, and related slip angle (angle of motion relative to tire), describe the performance of an individual tire. Important concepts about slip and skid include circle of forces or circle of traction, and cornering force. To a first approximation, the tire can withstand approximately the same absolut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drifting (motorsport)
Drifting is a driving technique where the driver intentionally oversteers, with loss of traction, while maintaining control and driving the car through the entirety of a corner. The technique causes the rear slip angle to exceed the front slip angle to such an extent that often the front wheels are pointing in the opposite direction to the turn (e.g. car is turning left, wheels are pointed right or vice versa, also known as opposite lock or counter-steering). Drifting is traditionally done by clutch kicking (where the clutch is rapidly disengaged and re-engaged with the intention of upsetting the grip of the rear wheels), then intentionally oversteering and countersteering. This sense of ''drift'' is not to be confused with the ''four wheel drift'', a classic cornering technique established in Grand Prix and sports car racing. As a motoring discipline, drifting competitions were first popularized in Japan in the 1970s and further popularized by the 1995 manga series '' Initial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vehicle Dynamics
For motorized vehicles, such as automobiles, aircraft, and watercraft, 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. 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 Distribut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishtailing
Fishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low friction surfaces (sand, gravel, rain, snow, ice, etc.). Rear-drive vehicles with sufficient power can induce this loss of traction on any surface, which is called power-oversteer. During fishtailing, the rear end of the car skids to one side, which must be offset by the driver counter-steering, which is turning the front wheels in the same direction as the skid, (e.g. left if the rear swings left) and reducing engine power. Over-correction will result in a skid in the opposite direction; hence the name. Without a proper driver's reaction, the fishtailing vehicle will spin completely. Friction is the main reason this action is effective. If a car is moving across a surface in any direction other than the direction it is pointed, it is skidding (or sliding), and a sideways load is being imposed against the tires. This causes a lot of fricti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opposite Lock
Opposite lock, also commonly known as counter-steering, is a colloquial term used to mean the steering associated with the deliberate use of oversteer to turn a vehicle rapidly without losing momentum. It is typified by the classic rallying style of rear-wheel drive cars, where a car travels around a bend with a large drift angle. The terms "opposite lock" and "counter-steering" refer to the position of the steering wheel during the maneuver, which is turned in the opposite direction to that of the bend. The technique works best on loose or wet surfaces where the friction between the tires and the road is not too high, but can also be used on asphalt or other surfaces with high friction if the vehicle has enough power to maintain speed. Before entry to the bend, the car is turned towards the bend slightly, but quickly, so as to cause a rotating motion that induces the rear of the car to slide outwards. Power is applied which applies further sideways movement. At the same tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bundorf Analysis
A Bundorf analysis is a measure of the characteristics of a vehicle that govern its understeer balance. The understeer is measured in units of degrees of additional yaw per g of lateral acceleration. An imaginary example Hence the total under-steer is 11.0 deg/g minus 6.9 deg/g, or 4.1 deg/g. Negative values are over-steering, positive values are under-steering, for that axle. If the under-steer contribution of the rear axle is greater than that of the front axle you get negative under-steer, which is known as oversteer. The analysis is only applicable while the parameters remain constant, and thus only up to about 0.4 g. Explanation of terms Load transfer effect and cornering stiffness of tire. As load transfers across the vehicle the tire's ability to provide cornering force for a given slip angle changes. The latter is known as the cornering stiffness of the tire. See also Tire load sensitivity Aligning torque. The tire does not just generate a lateral force, it gener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nonlinear System
In mathematics and science, a nonlinear system is a system in which the change of the output is not proportional to the change of the input. Nonlinear problems are of interest to engineers, biologists, physicists, mathematicians, and many other scientists because most systems are inherently nonlinear in nature. Nonlinear dynamical systems, describing changes in variables over time, may appear chaotic, unpredictable, or counterintuitive, contrasting with much simpler linear systems. Typically, the behavior of a nonlinear system is described in mathematics by a nonlinear system of equations, which is a set of simultaneous equations in which the unknowns (or the unknown functions in the case of differential equations) appear as variables of a polynomial of degree higher than one or in the argument of a function which is not a polynomial of degree one. In other words, in a nonlinear system of equations, the equation(s) to be solved cannot be written as a linear combination of the un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camber Thrust
Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling tire due to its camber angle and finite contact patch. Camber thrust is generated when a point on the outer surface of a leaned and rotating tire, that would normally follow a path that is elliptical when projected onto the ground, is forced to follow a straight path while coming in contact with the ground, due to friction. This deviation towards the direction of the lean causes a deformation in the tire tread and carcass that is transmitted to the vehicle as a force in the direction of the lean. Camber thrust is approximately linearly proportional to camber angle for small angles, reaches its steady-state value nearly instantaneously after a change in camber angle, and so does not have an associated relaxation length. Bias-ply tires have been found to generate more camber thrust than radial tires. Camber stiffness is a parameter used to describe the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornering Force
Cornering force or side force is the lateral (i.e., parallel to wheel axis) force produced by a vehicle tire during cornering. Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length. Slip angle describes the deformation of the tire contact patch, and this deflection of the contact patch deforms the tire in a fashion akin to a spring. As with deformation of a spring, deformation of the tire contact patch generates a reaction force in the tire; the cornering force. Integrating the force generated by every tread element along the contact patch length gives the total cornering force. Although the term, "tread element" is used, the compliance in the tire that leads to this effect is actually a combination of sidewall deflection and deflection of the rubber within the contact patch. The exact ratio of sidewall compliance to tread compliance is a factor in tire c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self Aligning Torque
Self aligning torque, also known as aligning torque, aligning moment, SAT, or Mz, is the torque that a tire creates as it rolls along, which tends to steer it, i.e. rotate it around its vertical axis. In the presence of a non-zero slip angle, this torque tends to steer the tire toward the direction in which it is traveling, hence its name. The magnitude of this torque can be calculated as the product of the lateral force generated at the contact patch and the distance behind the wheel centre at which that force acts. This distance is known as the pneumatic trail. The steering torque around a non-vertical steer axis with non-zero mechanical trail is given by : (trail + pneumatic trail) · cos( caster angle) · ''F''''y''. Even if the slip angle and camber angle are zero, and the road is flat, this torque will still be generated due to asymmetries in the tire's construction and the asymmetrical shape and pressure distribution o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weight Transfer
Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mass (CoM) location relative to the wheels because of suspension compliance or cargo shifting or sloshing In the automobile industry, weight transfer customarily refers to the change in load borne by different wheels during acceleration. This would be more properly referred to as load transfer, and that is the expression used in the motorcycle industry, while weight transfer on motorcycles, to a lesser extent on automobiles, and cargo movement on either is due to a change in the CoM location relative to the wheels. This article uses this latter pair of definitions. Load transfer In wheeled vehicles, load transfer is the measurable change of load borne by different wheels during acceleration (both longitudinal and lateral). This includes bra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SAE International
SAE International, formerly named the Society of Automotive Engineers, is a United States-based, globally active professional association and standards developing organization for engineering professionals in various industries. SAE International's world headquarters is in Warrendale, Pennsylvania, 20 miles north of Pittsburgh, Pennsylvania. Principal emphasis is placed on global transport industries such as aerospace, automotive, and commercial vehicles. The organization adopted the name SAE International to reflect the broader emphasis on mobility. SAE International has over 138,000 global members. Membership is granted to individuals, rather than companies. Aside from its standardization efforts, SAE International also devotes resources to projects and programs in STEM education, professional certification, and collegiate design competitions. For historical legacy reasons, the label "SAE" is commonly used on tools and hardware in North America to indicate United States ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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