Steering is a system of components, linkages, and other parts that allows a driver to control the direction of the vehicle.
Introduction
The most conventional steering arrangement allows a driver to turn the front wheels of a vehicle using a hand–operated
steering wheel
A steering wheel (also called a driving wheel (UK), a hand wheel, or simply wheel) is a type of steering control in vehicles.
Steering wheels are used in most modern land vehicles, including all mass-production automobiles, buses, light and ...
positioned in front of the driver. The steering wheel is attached to a steering
column
A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. ...
, which is linked to rods, pivots and gears that allow the driver to change the direction of the front wheels. Other arrangements are sometimes found on different types of vehicles; for example, a
tiller
A tiller or till is a lever used to steer a vehicle. The mechanism is primarily used in watercraft, where it is attached to an outboard motor, rudder post or stock to provide leverage in the form of torque for the helmsman to turn the rudder. ...
or rear-wheel steering.
Tracked vehicle
Continuous track is a system of vehicle propulsion used in tracked vehicles, running on a continuous band of treads or track plates driven by two or more wheels. The large surface area of the tracks distributes the weight of the vehicle b ...
s such as bulldozers and tanks usually employ
differential steering
Differential steering is the means of steering a land vehicle by applying more drive torque to one side of the vehicle than the other. Differential steering is the primary means of steering tracked vehicles, such as tanks and bulldozers, is als ...
, where the tracks are made to move at different speeds or even in opposite directions, using clutches and brakes, to achieve a change of direction.
Land vehicle steering
Basic geometry
Ackerman Steering Linkage.gif, Ackermann steering
Bell-Crank Steering Linkage.gif, Bell-crank steering
Rack-And-Pinion Steering Linkage.gif, Rack-and-pinion steering
Short rack steering.gif, Short rack-and-pinion steering
![Caster angle](https://upload.wikimedia.org/wikipedia/commons/f/f8/Caster_angle.svg)
The basic aim of steering is to ensure that the wheels are pointing in the desired directions to move the vehicle as required. This is typically achieved by a series of linkages, rods, pivots and gears. One of the fundamental concepts is that of
caster angle
250px, θ is the caster angle, the red line is the pivot line, and the grey area is the tire.
250px, Front suspension of a race car, the caster angle is formed by the line between upper and lower ball joint.
The caster angle or castor angle is t ...
. Each wheel is steered with a pivot point ahead of the wheel, which tends to make the steering self-centering towards the direction of travel.
The steering linkages connecting the steering box and the wheels usually conform to a variation of
Ackermann steering geometry
The Ackermann steering geometry is a geometric arrangement of linkages in the steering of a car or other vehicle designed to solve the problem of wheels on the inside and outside of a turn needing to trace out circles of different radii.
It was ...
, to account for the fact that in a turn, the inner wheel travels a path of smaller radius than the outer wheel, so that the degree of
toe
Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plan ...
suitable for driving in a straight path is not suitable for turns. The angle the wheels make with the vertical plane, known as
camber angle
Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering an ...
, also influences steering dynamics as do the tires.
Rack and pinion, recirculating ball, worm and sector
![Steer system](https://upload.wikimedia.org/wikipedia/commons/b/be/Steer_system.jpg)
Many modern cars use
rack and pinion
A rack and pinion is a type of linear actuator that comprises a circular gear (the '' pinion'') engaging a linear gear (the ''rack''). Together, they convert rotational motion into linear motion. Rotating the pinion causes the rack to be driven ...
steering mechanisms. When the steering wheel turns the pinion gear, the pinion moves the rack, converting circular motion into linear motion along the transverse axis of the car (side to side motion), kind of like a gear mechanism. This motion applies steering torque to the swivel pin
ball joint
In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles, and are used on virtually every automobile made. They bionically resemble the ball-and-socket joints found in most tetrapod animals. ...
s (that replaced previously used
kingpins) of the stub axle of the steered wheels via
tie rod
A tie rod or tie bar (also known as a hanger rod if vertical) is a slender structural unit used as a tie and (in most applications) capable of carrying tensile loads only.
It is any rod or bar-shaped structural member designed to prevent the separa ...
s and a short lever arm called the steering arm.
The rack and pinion design has the advantages of a direct steering "feeling".
BMW began to use rack and pinion steering systems in the 1930s with many other European manufacturers later adopting the technology. American automakers adopted rack and pinion steering beginning with the 1974
Ford Pinto
The Ford Pinto is a subcompact car that was manufactured and marketed by Ford Motor Company in North America from 1971 until 1980 model years. The Pinto was the first subcompact vehicle produced by Ford in North America.
The Pinto was marketed ...
.
Older designs use two main principles: the worm and sector design and the screw and nut. Both types were enhanced by reducing the friction; for screw and nut it is the
recirculating ball
Recirculating ball, also known as recirculating ball and nut or worm and sector, is a steering mechanism commonly found in older automobiles, off-road vehicles, and some trucks. Most newer cars use the more economical rack and pinion steering ins ...
mechanism, which is still found on trucks and utility vehicles. The steering column turns a large screw, which meshes with the nut by recirculating balls. The nut moves a sector of a gear, causing it to rotate about its axis as the screw is turned; an arm attached to the axis of the sector moves the
Pitman arm
A Pitman arm is a shaft that translates rotary or angular movement into linear movement, or vice versa. Pitman arms are commonly found in water pumping windmills, automotive steering systems, and sewing machines.
In windmills, the Pitman arm con ...
, which is connected to the steering linkage and thus steers the wheels. The recirculating ball version of this apparatus reduces the considerable friction by placing large ball bearings between the screw and the nut; at either end of the apparatus the balls exit from between the two pieces into a channel internal to the box, which connects them with the other end of the apparatus; thus, they are "recirculated".
The recirculating ball mechanism has the advantage of a much greater mechanical advantage, so that it was found on larger, heavier vehicles while the rack and pinion was originally limited to smaller and lighter ones; due to the almost universal adoption of
power steering
A power steering is a mechanical device equipped on a motor vehicle that helps drivers steer the vehicle by reducing steering effort needed to turn the steering wheel, making it easier for the vehicle to turn or maneuver at lower speeds.
Hydraul ...
, however, this is no longer an important advantage, leading to the increasing use of rack and pinion on newer cars. The recirculating ball design also has a perceptible lash, or "dead spot" on center, where a minute turn of the steering wheel in either direction does not move the steering apparatus; this is easily adjustable via a screw on the end of the steering box to account for wear, but it cannot be eliminated because it will produce excessive internal forces at other positions and the mechanism will wear very rapidly. This design is still in use in trucks and other large vehicles, where rapidity of steering and direct feel are less important than robustness, maintainability, and mechanical advantage.
The worm and sector was an older design, used for example in Willys and Chrysler vehicles, and the Ford Falcon (1960s). To reduce friction, the sector is replaced by a roller or rotating pins on the rocker shaft arm.
Generally, older vehicles use the recirculating ball mechanism, and only newer vehicles use rack-and-pinion steering. This division is not very strict, however, and rack-and-pinion steering systems can be found on British sports cars of the mid-1950s, and some German carmakers did not give up recirculating ball technology until the early 1990s.
Other systems for steering exist, but are uncommon on road vehicles. Children's toys and
go-kart
A go-kart, also written as go-cart (often referred to as simply a kart), is a type of sports car, close wheeled car, open-wheel car or quadracycle. Go-karts come in all shapes and forms, from non-motorised models to high-performance Kart rac ...
s often use a very direct
linkage
Linkage may refer to:
* ''Linkage'' (album), by J-pop singer Mami Kawada, released in 2010
*Linkage (graph theory), the maximum min-degree of any of its subgraphs
*Linkage (horse), an American Thoroughbred racehorse
* Linkage (hierarchical cluster ...
in the form of a
bellcrank
A bellcrank is a type of crank that changes motion through an angle. The angle can be any angle from 0 to 360 degrees, but 90 degrees and 180 degrees are most common. The name comes from its first use, changing the vertical pull on a rope to a h ...
(also commonly known as a Pitman arm) attached directly between the steering column and the steering arms, and the use of cable-operated steering linkages (e.g. the
capstan and bowstring
The Capstan and Bowstring is a mechanism that converts rotary motion into linear motion and vice versa. It is very similar in function to a rack and pinion but operates on a different principle, being that of the pole lathe. It consists of a caps ...
mechanism) is also found on some home-built vehicles such as
soapbox car
A gravity racer or soapbox is a motorless vehicle which is raced on a downhill road either against the clock or against another competitor. Although most are built for the purpose of recreation, some gravity racing teams take the sport more s ...
s and
recumbent tricycle
A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Most recumbent riders choose this type of design for ergonomic reasons: the rider's weight is distributed comfortably over a larger area, supported by ba ...
s.
Power steering
Power steering helps the driver of a vehicle to steer by directing some of its engine power to assist in swiveling the steered road wheels about their steering axes. As vehicles have become heavier and switched to
front-wheel drive
Front-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 longit ...
, particularly using negative offset geometry, along with increases in tire width and diameter, the effort needed to turn the wheels about their steering axis has increased, often to the point where major physical exertion would be needed were it not for power assistance. To alleviate this, auto makers have developed power steering systems, or more correctly power-assisted steering, since on road-going vehicles there has to be a mechanical linkage as a
fail-safe
In engineering, a fail-safe is a design feature or practice that in the event of a specific type of failure, inherently responds in a way that will cause minimal or no harm to other equipment, to the environment or to people. Unlike inherent safe ...
. There are two types of power steering systems: hydraulic and electric/electronic. A hydraulic-electric hybrid system is also possible.
A hydraulic power steering (HPS) uses hydraulic pressure supplied by an engine-driven pump to assist the motion of turning the steering wheel. Electric power steering (EPS) is more efficient than hydraulic power-steering, since the electric power-steering motor only needs to provide assistance when the steering wheel is turned, whereas the hydraulic pump must run constantly. In EPS, the amount of assistance is easily tunable to the vehicle type, road speed, and driver preference. An added benefit is the elimination of the environmental hazard posed by leakage and disposal of hydraulic power-steering fluid. In addition, electrical assistance is not lost when the engine fails or stalls, whereas hydraulic assistance stops working if the engine stops, making the steering doubly heavy as the driver must now turn not only the very heavy steering—without any help—but also the power-assistance system itself.
Speed-sensitive steering
A development of power steering is speed-sensitive steering, where the steering is heavily assisted at low speed and lightly assisted at high speed. Auto makers perceive that motorists might need to make large steering inputs while maneuvering for parking, but not while traveling at high speed. The first vehicle with this feature was the
Citroën SM
The Citroën SM is a high-performance coupé produced by the French manufacturer Citroën from 1970 to 1975. The SM placed third in the 1971 European Car of the Year contest, trailing its stablemate Citroën GS, and won the 1972 ''Motor Tre ...
with its
Diravi
DIRAVI is the name given by Citroën to its proprietary power steering system, first seen in 1970.
DIRAVI is an acronym for "''Direction à rappel asservi''" literally meaning "steering with controlled return" more accurately described in English ...
layout, although rather than altering the amount of assistance as in modern power steering systems, it altered the pressure on a centering cam which made the steering wheel try to "spring" back to the straight-ahead position. Modern speed-sensitive power steering systems reduce the mechanical or electrical assistance as the vehicle speed increases, giving a more direct feel. This feature is gradually becoming more common.
Four-wheel steering
200px, Sierra Denali with , rear steering angle.">Quadrasteer, rear steering angle.
![Slurry applicator - geograph](https://upload.wikimedia.org/wikipedia/commons/4/40/Slurry_applicator_-_geograph.org.uk_-_1252279.jpg)
Four-wheel steering is a system employed by some vehicles to improve steering response, increase vehicle stability while maneuvering at high speed, or to decrease
turning radius
The turning diameter of a vehicle is the minimum diameter (or "width") of available space required for that vehicle to make a circular turn (i.e. U-turn). The term thus refers to a theoretical minimal circle in which for example an aeroplane, a ...
at low speed.
Active four-wheel steering
In an active four-wheel steering system, all four wheels turn at the same time when the driver steers. In most active four-wheel steering systems, the rear wheels are steered by a computer and actuators.
The rear wheels generally cannot turn as far as the front wheels. There can be controls to switch off the rear steering and options to steer only the rear wheels independently of the front wheels. At low speed (e.g. parking) the rear wheels turn opposite to the front wheels, reducing the turning radius, sometimes critical for large trucks, tractors, vehicles with trailers and passenger cars with a large wheelbase, while at higher speeds both front and rear wheels turn alike (electronically controlled), so that the vehicle may change position with less
yaw and improved build-up of the lateral acceleration, enhancing straight-line stability.
The "snaking effect" experienced during motorway drives while towing a travel trailer is thus largely nullified.
Four-wheel steering found its most widespread use in
monster truck
A monster truck is a specialized off-road vehicle with a heavy duty suspension, four-wheel steering, large-displacement V8 engines and oversized tires constructed for competition and entertainment uses. Originally created by modifying stock pic ...
s, where maneuverability in small arenas is critical, and it is also popular in large farm vehicles and trucks. Some of the modern European Intercity buses also utilize four-wheel steering to assist maneuverability in bus terminals, and also to improve road stability. Mazda were pioneers in applying four-wheel steering to automobiles, showing it on their 1984 Mazda MX-02 concept car, where the rear wheels counter-steered at low speeds.
Mazda proceeded to offer a version of this electronic four-wheel steering system on the
Mazda 626
__NOTOC__
Year 626 ( DCXXVI) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. The denomination 626 for this year has been used since the early medieval period, when the Anno Domini calendar e ...
and
MX6 in 1988. The first rally vehicle to use the technology was the
Peugeot 405 Turbo 16
The Peugeot 405 Turbo 16 is a coupé built by Peugeot Talbot Sport, derived from the Peugeot 405 and the Peugeot 205 Turbo 16 in 1988 for African rally raids. Driven by Ari Vatanen the four wheel drive car won the Paris Dakar rally in 1989 and ...
, which debuted at the 1988 Pikes Peak International Hill Climb.
Previously, Honda had four-wheel steering as an option in their 1987–2001
Prelude and Honda Ascot Innova models (1992–1996). General Motors offered Delphi's
Quadrasteer
Quadrasteer is the name of a four wheel steering system developed by Delphi Automotive while under the ownership of General Motors for use in automobiles. It was available as an option on GM's full-size pickup trucks and 2500 Suburbans for model ...
in their Silverado/Sierra and Suburban/Yukon. Due to low demand, GM discontinued the technology at the end of the 2005 model year. Nissan/Infiniti offer several versions of their
HICAS HICAS ''/hīkas/'' (High Capacity Actively Controlled Steering) is Nissan's rear wheel steering system found on cars ranging from the more recent Skyline and Fairlady Z (300ZX) iterations to smaller models like the Nissan Cefiro (A31), 240SX/ Silvi ...
system as standard or as an option in much of their line-up.
In the early 2000s, a new generation of four-wheel steering systems was introduced into the market. In 2001 BMW equipped the
E65 7 series with an all-wheel steering system (optional, called 'Integral Active Steering'), which is available on the current 5, 6, and 7 series,
as an option. Renault introduced an optional all-wheel steering called '4control'
in 2009, at first on the
Laguna GT, which is currently available on the
Talisman
A talisman is any object ascribed with religious or magical powers intended to protect, heal, or harm individuals for whom they are made. Talismans are often portable objects carried on someone in a variety of ways, but can also be installed perm ...
,
Mégane and
Espace
Espace may refer to:
*ESPACE, a complexity class in computational complexity theory
*Espace musique, a Canadian radio service
*Espace 2, a Swiss radio station
*Radio Espace, a French radio station
*Espace Group, a French media company
*Group Espace ...
vehicle lines. In 2013, Porsche introduced a system on the
911 Turbo as standard equipment. Since 2016, the
Panamera
The Porsche Panamera is a mid/full-sized luxury car (E-segment/F-segment in Europe) manufactured and marketed by German automobile manufacturer Porsche across two generations using a front-engine, rear or all-wheel drive configuration.
Porsc ...
has been offered with optional all-wheel steering. The 2014
Audi Q7
The Audi Q7 is a mid-size luxury crossover SUV made by the German manufacturer Audi, unveiled in September 2005 at the Frankfurt Motor Show. Production of this seven-seater SUV began in the autumn of 2005 at the Volkswagen Bratislava Plant in ...
was launched with an optional system. Also the Japanese OEMs offer luxury segment vehicles equipped with all-wheel steering, such as Infiniti on its QX70 model ('Rear Active Steering') and Lexus on the GS. Italian manufacturers have launched the technology in the model years 2016–17 with the
Ferrari F12tdf
The Ferrari F12berlinetta (Type F152) is a front mid-engine, rear-wheel-drive grand tourer produced by Italian automobile manufacturer Ferrari. The F12berlinetta debuted at the 2012 Geneva Motor Show, and replaced the 599 grand tourer. The n ...
, the
Ferrari GTC4Lusso
The Ferrari GTC4Lusso (Type F151M) is a four-seat grand tourer produced by Italian automobile manufacturer Ferrari. The GTC4Lusso is a successor to the Ferrari FF.
Models GTC4Lusso (2016–2020)
Like its predecessor, the GTC4Lusso is a 3-door s ...
as well as the
Lamborghini Aventador S Coupé.
=Crab steering
=
Crab steering is a special type of active four-wheel steering. It operates by steering all wheels in the same direction and at the same angle. Crab steering is used when the vehicle needs to proceed in a straight line but at an angle: when changing lanes on a highway at speed, when moving loads with a reach truck, or during filming with a camera dolly.
Rear wheel steering can also be used when the rear wheels may not follow the path taken by the front wheel tracks (e.g. to reduce soil compaction when using rolling farm equipment).
Passive rear-wheel steering
Many modern vehicles have passive rear-wheel steering. On many vehicles, when cornering, the rear wheels tend to steer slightly to the outside of a turn, which can reduce stability. The passive steering system uses the lateral forces generated in a turn (through suspension geometry) and the
bushings to correct this tendency and steer the wheels slightly to the inside of the corner. This improves the stability of the car through the turn. This effect is called compliance
understeer
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 occu ...
; it, or its opposite, is present on all suspensions. Typical methods of achieving compliance understeer are to use a
Watt's link on a live rear axle, or the use of toe control bushings on a
twist beam suspension. On an
independent rear suspension
Independent suspension is any automobile suspension system that allows each wheel on the same axle to move vertically (i.e. reacting to a bump on the road) independently of the others. This is contrasted with a beam axle or deDion axle system in w ...
it is normally achieved by changing the rates of the rubber bushings in the suspension. Some suspensions typically have compliance
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 occu ...
due to geometry, such as
Hotchkiss live axles, semi-trailing arm IRS, and rear twist beams, but may be mitigated by revisions to the pivot points of the leaf spring or trailing arm, or additional suspension links, or complex internal geometry of the bushings.
Passive rear-wheel steering is not a new concept, as it has been in use for many years, although not always recognised as such.
Articulated steering
Articulated steering is a system by which a vehicle is split into front and rear halves which are connected by a vertical hinge. The front and rear halves are connected with one or more
hydraulic cylinder
A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment (engineering vehicles ...
s that change the angle between the halves, including the front and rear axles and wheels, thus steering the vehicle. This system does not use steering arms, king pins, tie rods, etc. as does four-wheel steering. If the vertical hinge is placed equidistant between the two axles, it also eliminates the need for a central
differential in four-wheel drive vehicles, as both front and rear axles will follow the same path, and thus rotate at the same speed.
Articulated hauler
An articulated hauler, articulated dump truck (ADT), or sometimes a dump hauler, is a very large heavy-duty type of dump truck used to transport loads over rough terrain, and occasionally on public roads. The vehicle usually has all-wheel drive and ...
s have very good off-road performance.
Vehicle-trailer-combinations such as semi-trailers,
road train
A road train, land train or long combination vehicle (LCV) is a trucking vehicle used to move road freight more efficiently than semi-trailer trucks. It consists of two or more trailers or semi-trailers hauled by a prime mover.
History
Early ...
s,
articulated bus
An articulated bus, also referred to as a banana bus, bendy bus, tandem bus, vestibule bus, wiggle wagon, stretch bus, or an accordion bus, (either a motor bus or trolleybus) is an articulated vehicle used in public transportation. It is usua ...
es, and internal transport trolley trains can be regarded as passively-articulated vehicles.
Rear-wheel steering
A few types of vehicle use only rear-wheel steering, notably
fork lift truck
A forklift (also called lift truck, jitney, hi-lo, fork truck, fork hoist, and forklift truck) is a powered industrial truck used to lift and move materials over short distances. The forklift was developed in the early 20th century by various ...
s,
camera dollies, early
pay loaders,
Buckminster Fuller
Richard Buckminster Fuller (; July 12, 1895 – July 1, 1983) was an American architect, systems theorist, writer, designer, inventor, philosopher, and futurist. He styled his name as R. Buckminster Fuller in his writings, publishing more t ...
's
Dymaxion car
The streamlined Dymaxion car was designed by American inventor Buckminster Fuller during the Great Depression and featured prominently at Chicago's 1933/1934 World's Fair. Fuller built three experimental prototypes with naval architect Star ...
, and the
ThrustSSC
ThrustSSC, Thrust SSC or Thrust SuperSonic Car is a British jet car developed by Richard Noble, Glynne Bowsher, Ron Ayers, and Jeremy Bliss.
Thrust SSC holds the world land speed record, set on 15 October 1997, and driven by Andy Green, w ...
.
In cars, rear-wheel steering tends to be unstable because, in turns, the steering geometry changes, hence decreasing the turn radius (oversteer), rather than increasing it (understeer). Rear-wheel steering is meant for slower vehicles that need high-maneuverability in tight spaces, e.g. fork lifts.
For heavy haulage or for increased manoeuvrability, some semi-trailers are fitted with rear-wheel steering, controlled electro-hydraulically. The wheels on all or some of the rear axles may be turned through different angles to enable tighter cornering, or through the same angle (crab steering) to move the rear of the trailer laterally.
Steer-by-wire
![Honda EV-STER twin-lever steering 2012 Tokyo Auto Salon](https://upload.wikimedia.org/wikipedia/commons/0/0f/Honda_EV-STER_twin-lever_steering_2012_Tokyo_Auto_Salon.jpg)
The aim of
steer-by-wire
Drive by wire, DbW, by-wire, steer-by-wire, fly-by-wire or x-by-wire technology in the automotive or aviation industry is the use of electrical or electro-mechanical systems for performing vehicle functions traditionally achieved by mechanical link ...
technology is to completely remove as many mechanical components (steering shaft, column, gear reduction mechanism, etc.) as possible. Completely replacing conventional steering system with steer-by-wire has several advantages, such as:
* The absence of steering column simplifies the car interior design.
* The absence of steering shaft, column and gear reduction mechanism allows much better space utilization in the engine compartment.
* The steering mechanism can be designed and installed as a modular unit.
* Without mechanical connection between the steering wheel and the road wheel, it is less likely that the impact of a frontal crash will cause the steering wheel to impact the driver.
* Steering system characteristics can easily be adjusted to change the steering response and feel.
As of 2020 there are no production cars available that rely solely on steer-by-wire technology due to safety, reliability and economic concerns, but this technology has been demonstrated in numerous
concept car
A concept car (also known as a concept vehicle, show vehicle or prototype) is a car made to showcase new styling and/or new technology. They are often exhibited at motor shows to gauge customer reaction to new and radical designs which may or ...
s and the similar ''
fly-by-wire
Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires, and flight control co ...
'' technology is in use in both military and civilian aviation applications.
Safety
For safety reasons all modern cars feature a collapsible steering column (energy absorbing steering column) which will collapse in the event of a heavy frontal impact to avoid excessive injuries to the driver.
Airbag
An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. Th ...
s are also generally fitted as standard. Non-collapsible steering columns fitted to older vehicles very often impaled drivers in frontal crashes, particularly when the steering box or rack was mounted in front of the front axle line, at the front of the
crumple zone
Crumple zones, crush zones, or crash zones are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in velocity (and consequently momentum) occurs from the impact during a collision by a ...
. This was particularly a problem on vehicles that had a rigid separate chassis frame with no crumple zone. Many modern vehicle steering boxes or racks are mounted behind the front axle on the front bulkhead, at the rear of the front crumple zone.
Collapsible steering columns were invented by
Béla Barényi
Béla Barényi (1 March 1907, Hirtenberg, Austro-Hungarian Monarchy – 30 May 1997, Böblingen, Germany) was an ethnic Hungarian engineer from Austria-Hungary, who was a prolific inventor, sometimes even compared to Thomas Edison. Barényi ...
and were introduced in the 1959
Mercedes-Benz W111
: ''See Mercedes-Benz S-Class for a complete overview of all S-Class models.''
The Mercedes-Benz W111 was a chassis code given to a range of Mercedes-Benz vehicles produced between 1959 and 1971, including four-door saloons (1959-1968) and two-d ...
Fintail, along with crumple zones. This safety feature first appeared on cars built by General Motors after an extensive and very public lobbying campaign enacted by
Ralph Nader
Ralph Nader (; born February 27, 1934) is an American political activist, author, lecturer, and attorney noted for his involvement in consumer protection, environmentalism, and government reform causes.
The son of Lebanese immigrants to the Un ...
. Ford started to install collapsible steering columns in 1968.
Audi used a retractable steering wheel and seat belt tensioning system called
procon-ten
procon-ten (lower case initial ''"p"'') (an acronym for ''Programmed Contraction-Tension'') is a proprietary ''Safety Restraint System'' (SRS), used by German car manufacturer Audi from 1986 until the mid-1990s.
Audi was one of the last German ...
, but it has since been discontinued in favor of airbags and pyrotechnic seat belt pre-tensioners.
Cycles
Differential steering
Differential steering is the primary means of steering
tracked vehicle
Continuous track is a system of vehicle propulsion used in tracked vehicles, running on a continuous band of treads or track plates driven by two or more wheels. The large surface area of the tracks distributes the weight of the vehicle b ...
s, such as tanks and bulldozers; it is also used in certain wheeled vehicles commonly known as
skid-steer
A skid loader, skid-steer loader, SSLs or skidsteer is a small, rigid-frame, engine-powered machine with lift arms that can attach to a wide variety of buckets and other labor-saving tools or attachments.
Skid-steer loaders are typically four-whee ...
s, and implemented in some automobiles, where it is called
torque vectoring
Torque vectoring is a technology employed in automobile differentials that has the ability to vary the torque to each half-shaft with an electronic system; or in rail vehicles which achieve the same using individually motored wheels. This method ...
, to augment steering by changing wheel direction relative to the vehicle.
Regulations
In the European Union, Russia and Japan, UNECE regulation 79 is related to steering.
In the United States,
Federal Motor Vehicle Safety Standards
The Federal Motor Vehicle Safety Standards (FMVSS) are U.S. federal vehicle regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated automobile safety-related components, systems, and d ...
203 and 204 are related to impact protection for the driver from the steering control system and steering control rearward displacement while 49
Code of Federal Regulations
In the law of the United States, the ''Code of Federal Regulations'' (''CFR'') is the codification of the general and permanent regulations promulgated by the executive departments and agencies of the federal government of the United States. ...
§ 393.209 is related to steering wheel systems.
Watercraft steering
Ships and boats are usually steered with a
rudder
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...
. Depending on the size of the vessel, rudders can be manually actuated, or operated using a
servomechanism
In control engineering a servomechanism, usually shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the action of a mechanism. On displacement-controlled applications, it usually includes a built-in ...
, or a
trim tab
Trim tabs are small surfaces connected to the trailing edge of a larger control surface on a boat or aircraft, used to control the trim of the controls, i.e. to counteract hydro- or aerodynamic forces and stabilise the boat or aircraft in a pa ...
or
servo tab
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A servo tab is a small hinged device installed on an aircraft control surface to assist the movement of the control surfaces. Introduced by the German firm Flettner, servo tabs were formerly known as Flettner tabs. Servo tabs are not ...
system. Boats using
outboard motor
An outboard motor is a propulsion system for boats, consisting of a self-contained unit that includes engine, gearbox and propeller or jet drive, designed to be affixed to the outside of the transom. They are the most common motorised method ...
s steer by rotating the entire drive unit. Boats with inboard motors sometimes steer by rotating the propeller pod only (i.e. Volvo Penta IPS drive). Modern ships with diesel-electric drive use
azimuth thruster
An azimuth thruster is a configuration of marine propellers placed in pods that can be rotated to any horizontal angle (azimuth), making a rudder unnecessary. These give ships better maneuverability than a fixed propeller and rudder system.
Ty ...
s. Boats power by
oar
An oar is an implement used for water-borne propulsion. Oars have a flat blade at one end. Rowers grasp the oar at the other end.
The difference between oars and paddles is that oars are used exclusively for rowing. In rowing the oar is connecte ...
s or
paddle
A paddle is a handheld tool with an elongated handle and a flat, widened distal end (i.e. the ''blade''), used as a lever to apply force onto the bladed end. It most commonly describes a completely handheld tool used to propel a human-powered wa ...
s are steered by generating a higher propulsion force on the side of the boat opposite of the direction of turn.
Jet ski
Jet Ski is the brand name of a personal watercraft (PWC) manufactured by Kawasaki, a Japanese company. The term is often used generically to refer to any type of personal watercraft used mainly for recreation, and it is also used as a verb to ...
s are steered by weight-shift induced roll and water jet
thrust vectoring
Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket, or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to control the attitude or angular velocity of the v ...
.
The rudder of a vessel can steer the ship only when water is passing over it. Hence, when a ship is not moving relative to the water it is in or cannot move its rudder, it does not respond to the helm and is said to have "lost steerage". The motion of a ship through the water is known as "making way". When a vessel is moving fast enough through the water that it turns in response to the helm, it is said to have "steerage way".
[
] That is why boats on rivers must always be under propulsion, even when traveling downstream.
Aircraft and hovercraft steering
Airplanes are normally steered when airborne by the use of
aileron
An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...
s,
spoileron
In aeronautics, spoilerons (also known as spoiler ailerons or roll spoilers) are spoilers that can be used asymmetrically as flight control surfaces to provide roll control.
Operation
Spoilerons roll an aircraft by reducing the lift of the down ...
s, or both to bank the aircraft into a turn; although the rudder can also be used to turn the aircraft, it is usually used to minimise
adverse yaw Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in lift and drag of each wing. The effect can be greatly minimized with ailerons deliberately designed to ...
, rather than as a means to directly cause the turn. On the ground, aircraft are generally steered at low speeds by turning the nosewheel or tailwheel (using a tiller or the rudder pedals) or through differential braking, and by the rudder at high speeds. Missiles, airships and large
hovercraft
A hovercraft, also known as an air-cushion vehicle or ACV, is an amphibious Craft (vehicle), craft capable of travelling over land, water, mud, ice, and other surfaces.
Hovercraft use blowers to produce a large volume of air below the hull ...
are usually steered by a rudder,
thrust vectoring
Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket, or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to control the attitude or angular velocity of the v ...
, or both. Small sport hovercraft have similar rudders, but steer mostly by the pilot shifting their weight from side to side and unbalancing the more powerful lift forces beneath the skirt. Jet packs and flying platforms are steered by thrust vectoring only.
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
s are steered by cyclic control, changing the thrust vector of the main rotor(s), and by anti-torque control, usually provided by a tail rotor.
See also
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Active Yaw Control (AYC)
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Bump Steer
Bump steer is the term for the tendency of the wheel of a car to steer itself as it moves through the suspension stroke.
Bump steer causes a vehicle to turn itself when one wheel hits a bump or falls down into a hole or rut. Excessive bump steer ...
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Camber angle
Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering an ...
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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 ...
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Caster angle
250px, θ is the caster angle, the red line is the pivot line, and the grey area is the tire.
250px, Front suspension of a race car, the caster angle is formed by the line between upper and lower ball joint.
The caster angle or castor angle is t ...
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Countersteering
Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn s ...
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DIRAVI
DIRAVI is the name given by Citroën to its proprietary power steering system, first seen in 1970.
DIRAVI is an acronym for "''Direction à rappel asservi''" literally meaning "steering with controlled return" more accurately described in English ...
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Dry steering
Dry steering is the act of turning the steering wheel of a vehicle while the vehicle is stationary.
This action can be exceptionally difficult in the absence of power steering
A power steering is a mechanical device equipped on a motor vehicle ...
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HICAS HICAS ''/hīkas/'' (High Capacity Actively Controlled Steering) is Nissan's rear wheel steering system found on cars ranging from the more recent Skyline and Fairlady Z (300ZX) iterations to smaller models like the Nissan Cefiro (A31), 240SX/ Silvi ...
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Kingpin
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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 s ...
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Power steering
A power steering is a mechanical device equipped on a motor vehicle that helps drivers steer the vehicle by reducing steering effort needed to turn the steering wheel, making it easier for the vehicle to turn or maneuver at lower speeds.
Hydraul ...
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Skid steer
A skid loader, skid-steer loader, SSLs or skidsteer is a small, rigid-frame, engine-powered machine with lift arms that can attach to a wide variety of buckets and other labor-saving tools or attachments.
Skid-steer loaders are typically four-whee ...
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Steer-by-wire
Drive by wire, DbW, by-wire, steer-by-wire, fly-by-wire or x-by-wire technology in the automotive or aviation industry is the use of electrical or electro-mechanical systems for performing vehicle functions traditionally achieved by mechanical link ...
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Steering damper
Originally designed in 1966 by Leonard R Jordan Jr the steering damper, or steering stabiliser is a damping device designed to inhibit an undesirable, uncontrolled movement or oscillation of a vehicle steering mechanism, a phenomenon known in moto ...
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Steering kickback
Steering kickback relates to the sharp and rapid movements of an automobile's steering wheel as the front wheels encounter a significant obstruction or imperfection in the road. The amount of kickback is dependent on a variety of factors, namely th ...
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Steering ratio Steering ratio refers to the ratio between the turn of the steering wheel (in degrees) or handlebars and the turn of the wheels (in degrees).
The steering ratio is the ratio of the number of degrees of turn of the steering wheel to the number of de ...
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Steering wheel
A steering wheel (also called a driving wheel (UK), a hand wheel, or simply wheel) is a type of steering control in vehicles.
Steering wheels are used in most modern land vehicles, including all mass-production automobiles, buses, light and ...
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Steering wheel (ship)
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Tiller
A tiller or till is a lever used to steer a vehicle. The mechanism is primarily used in watercraft, where it is attached to an outboard motor, rudder post or stock to provide leverage in the form of torque for the helmsman to turn the rudder. ...
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Torque steering
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of the ...
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Turning radius
The turning diameter of a vehicle is the minimum diameter (or "width") of available space required for that vehicle to make a circular turn (i.e. U-turn). The term thus refers to a theoretical minimal circle in which for example an aeroplane, a ...
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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 ...
References
* ''Encyclopedia of German Tanks of World War Two'' by Peter Chamberlain and Hilary Doyle, 1978, 1999
External links
How Car Steering Worksat
HowStuffWorks
HowStuffWorks is an American commercial infotainment website founded by professor and author Marshall Brain, to provide its target audience an insight into the way many things work. The site uses various media to explain complex concepts, termin ...
2000 technical paper on the kinematic design of rack-and-pinion steering linkages2002 technical paper on the kinematic design of bellcrank steering linkages
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Automotive steering technologies
Articles containing video clips
Vehicle dynamics