Cruise Control System

Cruise control is an important feature makes long road trips efficient and helpful for those of us suffering from lead-foot syndrome. It is far more common on American cars than European cars, because the roads in America are generally bigger and straighter, and destinations are farther apart.

As traffic continually increasing, basic cruise control is becoming less useful, but instead of becoming obsolete, cruise control systems are adapting to this new reality. Soon, cars will be equipped with adaptive cruise control, which will allow your car to follow the car in front of it while continually adjusting speed to maintain a safe distance.

The cruise control system actually has a lot of functions other than controlling the speed of your car. For instance, it can accelerate or decelerate the car by 1 mph with the tap of a button. Hit the button five times to go 5 mph faster. There are also several important safety features like disengage of cruise control as soon as you hit the brake pedal, and it won’t engage at speeds less than 40 kmph.

Cruise Internal Working

The cruise control system controls the speed of your car the same way you do, by adjusting the throttle position. But cruise control actuates the throttle valve by a cable connected to an actuator, instead of by pressing a pedal. The throttle valve controls the power and speed of the engine by limiting how much air the engine takes in. Many cars use actuators powered by engine vacuum to open and close the throttle. These systems use a small, electronically-controlled valve to regulate the vacuum in a diaphragm as shown in picture below.

Cruise

The throttle body connected through a cable to an actuator. Cruise controlled car consists of two cables connected to the throttle linkage, one is the Gas control cable and the other is the cruise control cable. This CC cable is connected to an actuator (Vacuum type) with piston in it. Vacuum actuator is built with vacuum in one side of the piston and the other side is open to atmosphere. This actuator is linked to valve that generates vacuum and is controlled by Electronic control unit.

Cruise Logic

  1. Switch ON the Cruise by setting some speed (Programmed speed)
  2. Speed sensor that compares the programmed speed with vehicle speed.
  3. If the vehicle speed is above the programmed speed, The Vacuum decreased in actuator and pulls the piston results in Slowing down the car.
  4. The vehicle speed is below the programmed speed, The Vacuum increased in actuator and pushes the piston results in Speeding up the car.

Adaptive Cruise Control

Adaptive cruise control (ACC) 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.

acc

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 ACC feature is just a preview of the technology being developed by the leading companies. These systems are being enhanced to include collision warning capabilities that will warn drivers through visual and/or audio signals that a collision is imminent and that braking or evasive steering is needed.