adaptive cruise control

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How Does Adaptive Cruise Control Work?

Ever since Karl Benz invented the first horseless carriage, auto manufacturers have used new technology to improve the safety and convenience of their vehicles. Seat belts were one of the first new pieces of safety technology added to vehicles, with future passive systems such as air bags and crumple zones added as manufacturers researched new technologies to keep passengers safe.

As computers have become smarter and more integrated into vehicles, auto manufacturers have also used these new devices to give drivers powerful new safety tools. From backup cameras to blind spot warning systems, these new technologies have helped prevent many accidents. Adaptive cruise control is one of the newest systems designed to keep drivers safe, and it has quickly become an essential feature for many drivers. What is adaptive cruise control, what makes it different from regular cruise control and why so many drivers like this new technology will be some of the questions answered in this article.

What is Adaptive Cruise Control?

how does adaptive cruise control work

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Adaptive cruise control, or ACC, is an intelligent and adaptable version of the cruise control system that cars have had for decades. Unlike regular cruise control systems, which simply hold the vehicle’s speed at a constant level, adaptive systems regulate the speed of the vehicle to maintain a safe following distance while in traffic. When the vehicle in front of your car brakes, your ACC system will slow down your vehicle as well; when the other vehicle accelerates, yours will too.

Today’s ACC systems don’t rely on external systems, such as roadside infrastructure or satellite communications, to maintain their speed. Instead, they use onboard computers and sophisticated sensors, such as radar systems, to monitor the other vehicles on the road. Because of this, adaptive cruise control is also called radar cruise control or autonomous cruise control.

The most common ACC systems are called assistive systems; they assist the driver, but they don’t use sensors from outside of the vehicle. Two other types are in development: multi-sensor systems and cooperative systems. Multi-sensor systems use external systems, such as GPS satellites, to provide additional information to the vehicle, allowing it to make more intelligent decisions. Cooperative ACC systems would communicate with other vehicles, allowing all of the vehicles to react almost instantaneously to each other.

What Does Adaptive Cruise Control Do?

Once the driver locks his preferred speed into his ACC system, the vehicle will monitor its surroundings. The system runs a signal from its radar headway system through a digital signal processor to determine the distance to the nearest car, and it then uses a longitudinal controller to determine a safe following distance. If the driver’s vehicle exceeds that following distance, the ACC system sends a signal to the engine or brakes, slowing the vehicle down. Once the path is clear, the ACC system will accelerate the vehicle back to the driver’s preferred speed.

History of Adaptive Cruise Control

adaptive cruise control

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Adaptive cruise control has been a fixture of vehicles for years, although early systems only warned drivers and didn’t directly control the speed of the vehicle. Mitsubishi introduced the first precursor to ACC in 1992 with its lidar-based Distance Warning system on the Japanese Debonair. Later, in 1995, Mitsubishi also introduced its laser-based Preview Distance Control, which could use throttle control or downshifting to influence the speed of the vehicle.

In 1999, Mercedes introduced the first radar-based ACC system, the Distronic. By this point, both lidar and radar systems were seeing active use, and manufacturers had begun giving these systems some amount of speed control. However, until 2000, all of these systems were exclusive to the overseas market; the first laser-based ACC, the Lexus Dynamic Laser Cruise Control system, was introduced to the American market that year. In 2005, the first American radar-based system was introduced as part of Acura’s collision avoidance system.

In 2006, Toyota introduced ACC systems that could operate across a wide range of speeds; before then, ACC systems were constrained to speeds above 20 mph. Audi added GPS functionality to its ACC systems in 2010. Recently, in 2015, ACC moved into the world of light-duty trucks with the 2015 Ford F-150.

How Does Adaptive Cruise Control Work?

Adaptive cruise control is a natural evolution of the basic cruise control system common to most American cars. Like a regular cruise control system, an adaptive system receives a speed setting from the driver and uses internal sensors to regulate airflow to the engine. By restricting airflow to the engine when the vehicle is close to its speed setting, and increasing airflow when the vehicle is below its speed setting, the cruise control system helps the car maintain a near-constant speed.

Adaptive cruise control takes the technology a step further, using sensors to gather information from outside of the vehicle to adjust the speed. Most systems use either a radar system or a laser system to detect vehicles and other obstacles; radar systems have better performance in bad weather, and laser systems tend to be more affordable. The system itself is composed of several parts, each with its own task:

  • The ACC module processes sensor data to determine if there’s another vehicle in front of the car.
  • The engine control module regulates the engine throttle according to data from the ACC module and the instrument cluster.
  • The brake control module checks the vehicle’s speed and applies the brakes when necessary.
  • The instrument cluster relays information about the system back to the driver and sends information from the cruise switches to the ACC module and the engine control module.
  • The cruise switches receive input from the driver, turning the system on or off and setting the desired speed.
  • The brake switches monitor the braking system and disengage the cruise control system when the driver applies the brakes manually.
  • The brake lights illuminate when either the driver or the ACC system engages the brakes.

To use the ACC system, the driver sets a desired speed using the controls, along with a desired following time, and the ACC system handles the necessary adjustments to comply with the driver’s wishes. When the system detects a vehicle ahead of it, it locks onto the vehicle and attempts to maintain its exact following distance, up to the max speed specified by the driver. Many adaptive cruise control systems are paired with pre-crash warning systems; they’ll alert the driver to a sudden change in the speed of the lead vehicle and warn them to apply the brakes immediately. Some systems will even apply emergency braking to avoid an accident.

Pros and Cons of Adaptive Cruise Control

Traditional cruise control is only viable in light traffic situations; when the driver must make frequent speed adjustments to compensate for traffic, cruise control becomes more of a hassle than a convenience. This is where adaptive cruise control systems really shine: with adaptive cruise control, drivers can take advantage of cruise control even in heavy traffic situations. Partial ACC systems can handle speeds down to about 20 mph, and full ACC systems are effective at almost any speed. Using such systems also helps the driver focus on the actual driving.

There are some disadvantages to adaptive cruise control systems. ACC systems are more expensive than traditional systems; an adaptive system will usually add at least $2,000 to the cost of the vehicle. Partial systems are cheaper, but they lack the full range of functional speeds of the more complete systems. In addition, the sensors on many ACC systems are sensitive to the weather and don’t work as well in rain or snow.

Further Developments

Manufacturers continue to make improvements to their adaptive cruise control systems. One hot research topic is the idea of cooperative cruise control, allowing vehicles to communicate with their neighbors, modulate their speeds and improve traffic flow.

Predictive cruise control is another avenue of research that is currently being pursued. Predictive systems would monitor vehicles in other lanes and anticipate the actions of those vehicles, adjusting for the possibility of a sudden lane change or mechanical failure.

In addition, adaptive cruise control systems are being incorporated into many new technologies, such as autonomous vehicles. However, many of these ideas will require standardization between manufacturers before drivers can truly see the benefits of these technologies.

Adaptive cruise control is a great feature that improves both safety and convenience.

By removing the burden of speed control from the driver, these systems allow humans to concentrate on other aspects of driving that require a clear head and decision making. As manufacturers continue to refine these systems and add new features to them, the safety benefits will only increase.


Does your new car have an adaptive cruise control system? What do you think about these systems?

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