Cruise control 1

Cruise control
Cruise control (sometimes known as speed control or
autocruise) is a system that automatically controls the
speed of a motor vehicle. The system takes over the
throttle of the car to maintain a steady speed as set by
the driver.

History
Speed control with a centrifugal governor was used in
automobiles as early as the 1910s, notably by Peerless.
Peerless advertised that their system would "maintain
speed whether up hill or down". The technology was
invented by James Watt and Matthew Boulton in 1788 Cruise control mounted on a 2000 Jeep Grand Cherokee Steering
Wheel
to control steam engines. The governor adjusts the
throttle position as the speed of the engine changes
with different loads.

Modern cruise control (also known as a speedostat) was invented in 1945 by the blind inventor and mechanical
engineer Ralph Teetor. His idea was born out of the frustration of riding in a car driven by his lawyer, who kept
speeding up and slowing down as he talked. The first car with Teetor's system was the Chrysler Imperial in 1958.
This system calculated ground speed based on driveshaft rotations and used a solenoid to vary throttle position as
needed.

Theory of operation
In modern designs, the cruise control may need to be turned on before use — in some designs it is always "on" but
not always enabled, others have a separate "on/off" switch, while still others just have an "on" switch that must be
pressed after the vehicle has been started. Most designs have buttons for "set", "resume", "accelerate", and "coast"
functions. Some also have a "cancel" button. Alternatively, depressing the brake or clutch pedal will disable the
system so the driver can change the speed without resistance from the system. The system is operated with controls
easily within the driver's reach, usually with two or more buttons on the steering wheel spokes or on the edge of the
hub like those on Honda vehicles, on the turn signal stalk like in many older General Motors vehicles or on a
dedicated stalk like those found in, particularly Toyota and Lexus. Earlier designs used a dial to set speed choice.
The driver must bring the vehicle up to speed manually and use a button to set the cruise control to the current speed.
The cruise control takes its speed signal from a rotating driveshaft, speedometer cable, wheel speed sensor from the
engine's RPM or from internal speed pulses produced electronically by the vehicle. Most systems do not allow the
use of the cruise control below a certain speed (normally around 25 mph/). The vehicle will maintain that speed by
pulling the throttle cable with a solenoid, a vacuum driven servomechanism or by using the electronic systems built
into the vehicle (fully electronic) if it uses a 'drive-by-wire' system.
All cruise control systems must be capable of being turned off both explicitly and automatically, when the driver
depresses the brake and often also the clutch. Cruise control often includes a memory feature to resume the set speed
after braking and a coast feature to disengage the system without braking. When the cruise control is engaged, the
throttle can still be used to accelerate the car, but once the pedal is released the car will then slow down until it
reaches the previously set speed.
Cruise control 2

On the latest vehicles fitted with electronic throttle control, cruise control can be easily integrated into the vehicle's
engine management system. Modern "adaptive" systems (see below) include the ability to automatically reduce
speed when the distance to a car in front, or the speed limit, decreases. This is an advantage for those driving in
unfamiliar areas.
The cruise control systems of some vehicles incorporate a "speed limiter" function, which will not allow the vehicle
to accelerate beyond a pre-set maximum; this can usually be overridden by fully depressing the accelerator pedal.
(Note that most systems will prevent the vehicle accelerating beyond the chosen speed, but will not apply the brakes
in the event of overspeeding downhill.)

Electronic Cruise Control

Daniel Aaron Wisner invented Automotive Electronic Cruise Control in 1968 as an engineer for RCA's Industrial
and Automation Systems Division in Plymouth, Michigan. His invention described in two patents filed that year
(#3570622 & #3511329), with the second modifying his original design by debuting digital memory, was the first
electronic gadgetry to play a role in controlling a car and ushered in the computer-controlled era in the automobile
industry. Two decades lapsed before an integrated circuit for his design was developed by Motorola Inc. as the
MC14460 Auto Speed Control Processor in CMOS. As a result, cruise control was eventually adopted by automobile
manufacturers as standard equipment and nearly every car built and many trucks are fitted with a configuration of
the circuitry and hardware nearly identical to his prototype. The advantage of electronic speed control over its
mechanical predecessor, which was featured on luxury models but never gained wide acceptance, was that it could
be easily integrated with electronic accident avoidance and engine management systems.

Advantages and disadvantages

Some of those advantages include:
• Its usefulness for long drives (reducing driver fatigue, improving comfort by allowing positioning changes more
safely) across Interstate highways and sparsely populated roads. This usually results in better fuel efficiency.
• Some drivers use it to avoid unconsciously violating speed limits. A driver who otherwise tends to unconsciously
increase speed over the course of a highway journey may avoid a speeding ticket. Such drivers should note,
however, that a cruise control may go over its setting on a downhill which is steep enough to accelerate with an
idling engine. Note however, that in many jurisdictions, officers cannot write a ticket for a violation of a speed
limit due to a steep hill.
However, cruise control can also lead to accidents due to several factors, such as:
• The lack of need to maintain constant pedal pressure, which can help lead to accidents caused by highway
hypnosis or incapacitated drivers; future systems may include a dead man's switch to avoid this.
• When used during inclement weather or while driving on wet or snow- and/or ice-covered roads, the vehicle
could go into a skid (although this may be somewhat mitigated by cars equipped with Electronic Stability
Control). Stepping on the brake — such as to disengage the cruise control — often results in the driver losing
control of the vehicle.
Driving over "rolling" terrain, with gentle up and down portions, can usually be done more economically (using less
fuel) by a skilled driver viewing the approaching terrain, by maintaining a relatively constant throttle position and
allowing the vehicle to accelerate on the downgrades and decelerate on upgrades, while reducing power when
cresting a rise and adding a bit before an upgrade is reached. Cruise control will tend to overthrottle on the upgrades
and retard on the downgrades, wasting the energy storage capabilities available from the inertia of the vehicle. The
inefficiencies from cruise control can be even greater relative to skilled driving in hybrid vehicles.
Many countries establish that it is illegal to drive within city limits with the cruise control feature activated.
Cruise control 3

Adaptive cruise control

Some modern vehicles have adaptive cruise control (ACC) systems, which is a general term meaning improved
cruise control. These improvements can be automatic braking or dynamic set-speed type controls.
Automatic Braking Type: The automatic braking type use either a radar or laser setup to allow the vehicle to keep
pace with the car it is following, slow when closing in on the vehicle in front and accelerating again to the preset
speed when traffic allows. Some systems also feature forward collision warning systems, which warns the driver if a
vehicle in front - given the speed of both vehicles - gets too close (within the preset headway or braking distance).
Dynamic Set Speed Type: The dynamic set speed uses the GPS position of speed limit signs, from a database. Some
are modifiable by the driver.

References

External links
• Overview of intelligent vehicle safety systems (http://www.esafetysupport.org/en/
learn_about_esafety_systems/)
• Intelligent Transport Systems (http://www.ertico.com/)
• Tempomat.ro - pilot automat pt gama auto VAG (http://www.tempomat.ro/)
• Preventive safety applications and technologies (http://prevent-ip.org/en/)
• Cruise [Un]Control: Driver sets the cruise control on his vehicle, then slips into the backseat for a nap (http://
www.snopes.com/autos/techno/cruise.asp) at Snopes.com
Article Sources and Contributors 4

Article Sources and Contributors

Cruise control  Source: http://en.wikipedia.org/w/index.php?oldid=393781461  Contributors: 777sms, Alansohn, Andres, Andrew123, AndrewHowse, Angr, Ap, Atomicblender, Bloodshedder,
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Image:2000 Jeep Steering Wheel.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:2000_Jeep_Steering_Wheel.jpg  License: GNU Free Documentation License  Contributors: User
Sav127 on en.wikipedia

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