What is cruise control in cars

Once you've selected the speed, you can take your foot off the accelerator and the vehicle will cruise at that speed. Cruise control is a feature that comes in handy when you drive at a constant speed. It is an electric system that allows you to set your car to a specific speed, letting you take your foot off the accelerator pedal.

So, it can ease foot-fatigue and stress over a long drive. Another great benefit to using cruise control is that you are going to have greater fuel efficiency. Your vehicle will consume much less fuel if you cruise at a steady speed rather than accelerating at each section of the open road.

Ultimately, it's not hard to save on fuel if you let your vehicle automatically maintain a steady cruising speed. The leading edge of cruise control today is adaptive cruise control. Almost all cars now will be equipped with this smart system. Just as conventional cruise control, adaptive cruise control allows you to set a desired travel speed. But the difference is that the adaptive cruise control maintains a safe distance between the car in front of you and your car at a consistent pace by using the forward-mounted sensors.

For instance, if the car ahead of your vehicle begins to slow, adaptive cruise control will use the engine brake to automatically slow the pace of your vehicle and maintain the selected distance.

Many say adaptive cruise control is a step to autonomous cars in the future. But it is not quite fully autonomous driving, since you have to keep your hands on the wheel and be fully cognizant of the road. Also, if you were on a steep enough hill, the car might not accelerate at all. Most cruise control systems use a control scheme called proportional-integral-derivative control a. PID control. Don't worry, you don't need to know any calculus to make it through this explanation -- just remember that:.

A PID control system uses these three factors -- proportional, integral and derivative, calculating each individually and adding them to get the throttle position.

We've already discussed the proportional factor. The integral factor is based on the time integral of the vehicle speed error. Translation: the difference between the distance your car actually traveled and the distance it would have traveled if it were going at the desired speed, calculated over a set period of time. This factor helps the car deal with hills, and also helps it settle into the correct speed and stay there. Let's say your car starts to go up a hill and slows down.

The proportional control increases the throttle a little, but you may still slow down. After a little while, the integral control will start to increase the throttle, opening it more and more, because the longer the car maintains a speed slower than the desired speed, the larger the distance error gets.

Now let's add in the final factor, the derivative. Remember that the derivative of speed is acceleration.

This factor helps the cruise control respond quickly to changes, such as hills. If the car starts to slow down, the cruise control can see this acceleration slowing down and speeding up are both acceleration before the speed can actually change much, and respond by increasing the throttle position. Two companies are developing a more advanced cruise control that can automatically adjust a car's speed to maintain a safe following distance. This new technology, called adaptive cruise control , uses forward-looking radar , installed behind the grill of a vehicle, to detect the speed and distance of the vehicle ahead of it.

Adaptive cruise control is similar to conventional cruise control in that it maintains the vehicle's pre-set speed. However, unlike conventional cruise control, this new system can automatically adjust speed in order to maintain a proper distance between vehicles in the same lane.

This is achieved through a radar headway sensor , digital signal processor and longitudinal controller. If the lead vehicle slows down, or if another object is detected, the system sends a signal to the engine or braking system to decelerate. Then, when the road is clear, the system will re-accelerate the vehicle back to the set speed. The GHz Autocruise radar system made by TRW has a forward-looking range of up to feet meters , and operates at vehicle speeds ranging from Delphi's GHz system can also detect objects as far away as feet, and operates at speeds as low as 20 mph 32 kph.

Adaptive cruise control is just a preview of the technology being developed by both companies. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Under the Hood. It is most useful on long drives on motorways or roads with less traffic as it reduces driver fatigue.

Drivers can easily shift into more comfortable positions without needing to keep their foot on the pedal. Cruise control is activated with a button or lever in the car cockpit, usually on the steering wheel. Repressing the button or pressing the brakes will turn off the system and put the driver back in control of the accelerator. Early cruise control While speed control was used in automobiles as far back as the beginning of the twentieth century, modern cruise control was invented in by the American engineer Ralph Teetor.

The idea came to him while riding as a passenger in a car driven by his lawyer, who kept speeding up and slowing down every time he talked. By the s, cars from every manufacturer featured a form of cruise control. LiDAR, radar, sonar and camera-based solutions have become a staple of modern cars, allowing them to sense other vehicles in order to determine speed, as well as detecting and avoiding collisions, maintaining lane positions and predicting the behaviour of other vehicles.

This goes further than standard cruise control by incorporating advanced safety features such as automatic braking. It uses front radar sensors to maintain a constant speed and distance from the vehicle ahead by automatically accelerating and braking. If the vehicle stops for longer than three seconds, the driver has to activate the system again with the steering wheel controls or by briefly pressing the accelerator pedal.

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