What is cruise control in autos
The majority of modern automobiles have several electronic innovations that were designed to improve our driving experience. One of the most popular automotive innovations is the cruise control system, which is used to regulate the speed of the vehicle most often while its driver is taking a long, tiring journey on highways and interstates.
How does the cruise control system work?
And why are we able to maintain a relatively even speed whether we travel up steep inclines or along flat interstates? In simple terms, a driver regulates the speed of a car by stepping on the gas pedal or applying pressure to the brakes. The cruise control system works in a similar way, except that it isn’t able to activate the brakes, just modulate the throttle.
The brain of the cruise control system is the electronic control module (or ECM). The speed of any vehicle is monitored by the vehicle speed sensor that is attached to the output shaft of the transmission. For every rotation of the shaft, the speed sensor gives off a pre-determined number of pulses.
The faster the vehicle goes, the quicker the pulses, the slower the speed, the greater the time between pulses. These pulses are sent to the ECM as well as the speedometer which displays the speed of the vehicle on the dash.
When the cruising speed on a vehicle is selected by the driver, the ECM records the frequency of pulses that corresponds with that speed. It is therefore this pulse frequency that the ECM uses as a benchmark when maintaining the car at a constant speed. After the ECM stores the desired pulse frequency in its memory, it constantly monitors the frequency of pulses coming from the vehicle speed sensor. If the frequency is ever different in value it causes the ECM to do one of two things: 1) apply more throttle 2) reduce the throttle
The ECM is able to adjust the amount of throttle applied to a vehicle as it controls an electronic vacuum actuator or servo that’s linked to the throttle mechanism. If the ECM detects a decrease in the pulse frequency from the speed sensor, it will send an electrical signal to the vacuum actuator to increase the vacuum force being applied to the throttle mechanism.
The electrical signal will continue until the pre-set cruising speed is reached. An example of when this might happen in real-world driving is when driving up a steady incline a car in cruise mode may initially start to lose some speed until the ECM responds by causing the car to accelerate until cruising speed is reached once more.
If the ECM ever detects an increase in the pulse frequency from the speed sensor, it will send an electrical signal to the vacuum actuator to reduce the force being applied to the throttle mechanism. The reduction in force will continue until the preset cruising speed is reached once more.
An example of when this happens in real-world driving is when descending down from an elevated hill a car in cruise mode will initially speed up as gravity will cause the car to accelerate. When the ECM reduces throttle input, eventually drag will cause the car to slow down again until the cruising speed is reached.
This is a basic overview of the cruise control system used in the majority of modern cars. These systems are constantly being developed and further updated by car manufacturers such as Lexus and Mercedes-Benz. An example of a technologically advanced cruise control system is where a laser is used to track the distance between your car and the nearest car directly in front of you.
If that distance ever decreases past a certain point, then not only is the vacuum force applied to the throttle mechanism stopped, but the brakes are applied to avoid a collision.