Cruise control (also known as speed control, cruise command, autocruise, or tempomat) is a system that automatically controls the

speed In kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a non-negative scalar quantity. Intro ...

of an

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

. The system is a

servomechanism In mechanical and control engineering, a servomechanism (also called servo system, or simply servo) is a control system for the position and its time derivatives, such as velocity, of a mechanical system. It often includes a servomotor, and ...

that takes over the car's

throttle A throttle is a mechanism by which fluid flow is managed by construction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ha ...

to maintain a steady speed set by the driver.

History

Speed control existed in early automobiles such as the Wilson-Pilcher in the early 1900s. They had a lever on the steering column that could be used to set the speed to be maintained by the engine. In 1908, the Peerless included a governor to keep the speed of the engine through an extra throttle lever on the steering wheel. Peerless successfully used a flyball governor. They advertised their system as being able to "maintain speed whether uphill or down." A governor was used by

James Watt James Watt (; 30 January 1736 (19 January 1736 OS) – 25 August 1819) was a Scottish inventor, mechanical engineer, and chemist who improved on Thomas Newcomen's 1712 Newcomen steam engine with his Watt steam engine in 1776, which was f ...

and

Matthew Boulton Matthew Boulton ( ; 3 September 172817 August 1809) was an English businessman, inventor, mechanical engineer, and silversmith. He was a business partner of the Scottish engineer James Watt. In the final quarter of the 18th century, the par ...

in 1788 to control

steam engine A steam engine is a heat engine that performs Work (physics), mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a Cylinder (locomotive), cyl ...

s, but the use of governors dates at least back to the 17th century. On an engine, the governor uses

centrifugal force Centrifugal force is a fictitious force in Newtonian mechanics (also called an "inertial" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It appears to be directed radially away from the axi ...

to adjust the throttle position to adapt the engine's speed to different loads (e.g., when going up a hill). Modern cruise control (also known as a speedostat or tempomat) was invented in 1948 by the blind inventor and mechanical engineer Ralph Teetor. He came up with the idea due to being frustrated by his driver's habit of speeding up and slowing down as he talked. A more significant factor in developing cruise control was the speed limit imposed in the United States during World War II to reduce gasoline use and tire wear. A mechanism controlled by the driver provided resistance to further pressure on the accelerator pedal when the vehicle reached the desired speed. Teetor's idea of a dashboard speed selector with a mechanism connected to the driveshaft and a device able to push against the gas pedal was patented in 1950. He added a speed lock capability that maintained the car's speed until the driver tapped the brake pedal or turned off the system. A 1955 U.S. patent for a "constant speed regulator" was filed in 1950 by M-Sgt Frank J. Riley. He conceived the device while driving on the Pennsylvania Turnpike and installed his invention in his car in 1948. Another inventor named Harold Exline, working independently of Riley, also invented a type of cruise control that he first installed on his car and friends' cars. Exline filed a U.S. patent for a "vacuum powered throttle control with electrically controlled air valve" in 1951, which was granted in 1956. Despite these patents, Riley, Exline, and subsequent patent holders were not able to collect royalties for any cruise control inventions. The first car with Teetor's "speedostat" system was the 1958

Chrysler Imperial The Chrysler Imperial, introduced in 1926, was Chrysler (division), Chrysler's top-of-the-line vehicle for much of its history. Models were produced under the Chrysler name until 1954, after which Imperial became Imperial (automobile), a standal ...

(called "auto-pilot"), using a speed control dial on the dashboard. This system calculated ground speed from the rotating speedometer cable and used a bi-directional screw-drive

electric motor An electric motor is a machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a electromagnetic coil, wire winding to gene ...

to vary the throttle position as needed. Cadillac soon renamed and marketed the device as "cruise control." In 1965,

American Motors Corporation American Motors Corporation (AMC; commonly referred to as American Motors) was an American automobile manufacturing company formed by the mergers and acquisitions, merger of Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1, 19 ...

(AMC) introduced a low-priced automatic speed control for its large-sized cars with automatic transmissions. The AMC "cruise command" unit was actuated through a push-button on the dashboard once the car's desired speed was reached. The throttle position was automatically adjusted by a vacuum control that opened and closed the throttle based on input from the speedometer cable rather than through an adjustable control on the dashboard. The unit would shut off anytime the brakes were applied. Daniel Aaron Wisner invented an "automotive electronic cruise control" in 1968 as an engineer for

RCA RCA Corporation was a major American electronics company, which was founded in 1919 as the Radio Corporation of America. It was initially a patent pool, patent trust owned by General Electric (GE), Westinghouse Electric Corporation, Westinghou ...

's Industrial and Automation Systems Division in

Plymouth, Michigan Plymouth is a city in Wayne County in the U.S. state of Michigan. A western suburb of Detroit, Plymouth is located roughly northwest of downtown Detroit, and northeast of Ann Arbor. As of the 2020 census, the city had a population of 9,370. ...

. His invention is described in two patents filed that year (US patents 3570622 and 3511329), with the second introducing digital memory, and was the first electronic device that controlled a car. Due to the

1973 oil crisis In October 1973, the Organization of Arab Petroleum Exporting Countries (OAPEC) announced that it was implementing a total oil embargo against countries that had supported Israel at any point during the 1973 Yom Kippur War, which began after Eg ...

and rising fuel prices, the device became more popular in the U.S. "Cruise control can save gas by avoiding surges that expel fuel" while driving at steady speeds. In 1974, AMC, GM, and Chrysler priced the option at $60 to $70, while Ford charged $103. In the late 1980s, an

integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

for Wisner's design for electronic cruise control was finally commercially developed by

Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois. It was founded by brothers Paul and Joseph Galvin in 1928 and had been named Motorola since 1947. Many of Motorola's products had been ...

as the MC14460 Automotive Speed Control Processor in

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss ", , ) is a type of MOSFET, metal–oxide–semiconductor field-effect transistor (MOSFET) semiconductor device fabrication, fabrication process that uses complementary an ...

. The advantage of electronic speed control over its mechanical predecessor was that it could be integrated with electronic accident avoidance and engine management systems.

Operation

Tempomat Cruise Control IMG 20170712 182317674

Tempomat Cruise Control IMG 20170712 182537172

The driver must manually bring the vehicle up to speed and use a button to set the cruise control to the current speed, except in the case of

adaptive cruise control Adaptive cruise control (ACC) is a type of advanced driver-assistance system for road vehicles that automatically adjusts the vehicle speed to maintain a safe distance from vehicles ahead. As of 2019, it is also called by 20 unique names that ...

. The cruise control takes its speed signal from a rotating

driveshaft A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power, torque, and rotation, usually used to connect ...

speedometer A speedometer or speed meter is a gauge (instrument), gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the early 20th century, and as ...

cable, wheel speed sensor from the engine's

RPM Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...

, or internal speed pulses produced electronically by the vehicle. Most systems do not allow the use of the cruise control below a certain speed - typically around . The vehicle will maintain the desired speed by pulling the

cable with a

solenoid upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whos ...

, a

vacuum A vacuum (: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective (neuter ) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressur ...

-driven

, 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 have the capability to be turned off explicitly and automatically when the driver depresses the brake pedal and often also the clutch. Cruise control systems frequently include a memory feature to resume the set speed after braking and a coast feature to reduce the set speed without braking. When the cruise control is engaged, the throttle can still accelerate the car, but once the pedal is released, it will slow down the vehicle until it reaches the previously set speed. On the latest vehicles fitted with

electronic throttle control Electronic throttle control (ETC) is an Automotive engineering, automotive technology that uses electronics to replace the traditional mechanical linkages between the driver's input such as a Car controls#Throttle control, foot pedal to the vehi ...

, cruise control can be integrated into the vehicle's

engine management system An engine control unit (ECU), also called an engine control module (ECM), is a device that controls various subsystems of an internal combustion engine. Systems commonly controlled by an ECU include the fuel injection and ignition systems. The ...

. Modern "adaptive" systems include the ability to automatically reduce speed when the distance to a car in front, or the speed limit, decreases. The cruise control systems of some vehicles incorporate a "speed limiter" function, which will not allow the vehicle to accelerate beyond a preset maximum; this can usually be overridden by fully depressing the accelerator pedal. Most systems will prevent the vehicle from increasing engine speed to accelerate beyond the chosen speed. However, they will not apply the brakes in the event of over-speeding downhill, nor stop the car from going faster than the selected speed even with the engine just idling. Cruise control is less flexible on vehicles with a

manual transmission A manual transmission (MT), also known as manual gearbox, standard transmission (in Canadian English, Canada, British English, the United Kingdom and American English, the United States), or stick shift (in the United States), is a multi-speed ...

because depressing the clutch pedal and shifting gears usually disengages the cruise control. The "resume" feature has to be used each time after selecting the new gear and releasing the clutch. Therefore, cruise control is most beneficial at

motorway A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway, and expressway. Other similar terms ...

/highway speeds when top gear is used virtually all the time. The speed limiter function, however, does not have this problem.

Advantages and disadvantages

Some advantages of cruise control include: * It is helpful for long drives along

highways A highway is any public or private road or other public way on land. It includes not just major roads, but also other public roads and rights of way. In the United States, it is also used as an equivalent term to controlled-access highway, or ...

and sparsely populated

road A road is a thoroughfare used primarily for movement of traffic. Roads differ from streets, whose primary use is local access. They also differ from stroads, which combine the features of streets and roads. Most modern roads are paved. Th ...

s by reducing driver fatigue and improving comfort by allowing positioning changes more safely. * Some drivers use it to avoid

speeding Speed limits on road traffic, as used in most countries, set the legal maximum speed at which vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum permitted speed, expre ...

, particularly those who may subconsciously increase speed during a long highway journey. * Increased

fuel efficiency Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical energy, chemical potential energy contained in a carrier (fuel) into kinetic energy or Mechanical work, w ...

However, when misused, cruise control can lead to accidents due to several factors, such as: * hazardous weather conditions. The U.S. state of Michigan warns against using cruise control if the road has ice or snow, while the Canadian province of British Columbia recommends not using cruise control on wet roads. In some older cars, if they skid with cruise control enabled, the vehicle will keep accelerating, increasing the chance of losing control. If the vehicle is sliding on ice, the driver should not brake or accelerate, but just let the vehicle slow down on its own. * speeding around curves that require slowing down * rough or loose terrain that could negatively affect the cruise control controls * Encourages drivers to pay less attention to driving, increasing the risk of an accident * Risk of sudden unintended acceleration (SUA) and possible accidents. Drivers with feet at rest lose spatial perception and may hit the accelerator instead of the brake pedal in a sudden emergency.

Adaptive cruise control

Some modern vehicles have adaptive cruise control (ACC) systems, a general term meaning improved cruise control. Dynamic set speed systems use the GPS position of

speed limit Speed limits on road traffic, as used in most countries, set the legal maximum speed at which vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum permitted speed, express ...

signs from a database. Many systems also incorporate cameras, lasers, and millimeter-wave

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

equipment to determine how close a vehicle is to others or other objects on the roadway. The technologies can be set to maintain a distance from vehicles in front of the car; the system will automatically slow down based on the vehicles in front or continue to keep the set speed. Some systems cannot detect completely stationary cars or pedestrians, so the driver must always pay attention. Automatic braking systems use either a single or a combination of sensors (radar, lidar, and camera) to allow the vehicle to keep pace with the car it is following, slow when closing in on the vehicle in front, and accelerate to the preset speed when traffic allows. Some systems also feature forward collision warning systems, which warn the driver if a vehicle in front—given the speed of both vehicles—gets too close within the preset headway or braking distance. Vehicles with adaptive cruise control are considered a Level 1

autonomous car A self-driving car, also known as an autonomous car (AC), driverless car, robotic car or robo-car, is a car that is capable of operating with reduced or no User input, human input. They are sometimes called robotaxi, robotaxis, though this te ...

, as defined by

SAE International SAE International is a global professional association and standards organization based in Warrendale, Pennsylvania, United States. Formerly the Society of Automotive Engineers, the organization adopted its current name in 2006 to reflect bot ...

References

External links

*
Cruise control block diagram

Overview of intelligent vehicle safety systems

Intelligent Transport Systems
*
Cruise Control as Auto-Pilot
at

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