Chapter 3 Cruise Control 06:59 Chapter 3 Cruise Control How Cruise Control Works LECTURER NAME: MR. KHAIRUL AKMAL BIN NUSI

INTRODUCTION The cruise control system actually has a lot of functions other than controlling the speed of your car. For instance, the cruise control 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 such as the cruise control will disengage as soon as you hit the brake pedal/clutch pedal and it won't engage at speeds less than 25 mph (40 kph). The system has five buttons: On, Off, Set/Acceleration, Resume and Coast. It also has a sixth control : the brake pedal, and if your car has a manual transmission the clutch pedal is also hooked up to the cruise control

Control system theory The system is operated with control buttons within easy reach drivers. Usually via the buttons on the steering wheel spokes or edge as the Honda vehicles, the turn signal stalk switch as in General Motors vehicles for longer, or at special stalk on Toyota vehicles , Lexus and Proton. Controller skating usually included with a memory feature to resume a set speed after braking and skating features to release the system without braking. During the slide controller is activated, the throttle can still be used to accelerate, but when the throttle pedal is released, the car will be slowed down until it reaches the speed set prior to it.

The latest modern technology will also include the ability to reduce speed when automatic when followed distance is reduced. It is an advantage for drivers who drive in unfamiliar areas. Some slide guard system has a "speed limiter", which does not allow the vehicle accelerated beyond the prescribed maximum speed, it can be formulated by pressing the throttle pedal completely.

Proportional control system In a proportional control system, the cruise control adjusts the throttle proportional to the error, the error being the difference between the desired speed and the actual speed. So, if the cruise control is set at 60 mph and the car is going 50 mph, the throttle position will be open quite far. When the car is going 55 mph, the throttle position opening will be only half of what it was before. The result is that the closer the car gets to the desired speed, the slower it accelerates. If climbing the hill, the car might not accelerate at all using this control system.

Proportional integral derivative control(PID control) Most cruise control systems use a control scheme called proportional-integral-derivative control(a.k.a. PID control). The proportional is the difference between the desired speed and the actual speed. The integral of speed is distance. The derivative of speed is acceleration. A PID control system uses these three factors : proportional, integral and derivative, calculating each individually and adding them to get the throttle position.

Integral of speed is distance The difference between the distance your car actually travelled and the distance it would have travelled 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.

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.

Adaptive cruise control Imagine driving your car in the highway whereby you could just step on the gas pedal with a constant amount of force or pressure and it will only reach the speed that you have set the car into? You could set the speed to say – 110 km/h and it will stick to that pace even if you step on the gas pedal at maximum level or touching down the floor.

This system is very useful as it allows your car to follow the vehicle in front while continuously adjusting the speed automatically which enables to maintain a safe distance. This system comes with a ‘radar’ sensor, ‘digital signal processor’ and ‘longitudinal controller’. Your car detects a vehicle in front using a radar sensor and automatically slows down or adjusts the speed to an appropriate distance using the ‘signal processor’ and ‘controller’ (mentioned earlier). Once the road is clear or the car in front has moved to a different lane, then your car will automatically accelerate to the speed it was set into.

Car manufacturers are still developing the system and soon this will include warning capabilities in which it will alert the driver of an collision either through audio or visual indication that avoid maneuver of steering wheel with brakes are needed. Another advantage of this system is that the driver will not exceed the speed limit on the highway.

Advantages and disadvantages Some of those advantages include: Its usefulness for long drives (reducing driver fatigue, improving comfort by allowing positioning changes more safely) across highways and sparsely populated roads. This usually results in better fuel efficiency. Some drivers use it to avoid unconsciously violating speed limits. A driver who otherwise tends to unconsciously increase speed over the course of a highway journey may avoid a speeding ticket. However, cruise control can also lead to accidents due to several factors, such as: The damage of the sensor. When used during inclement weather or while driving on wet or snow- and/or ice-covered roads, the vehicle could go into a skid (although this may be somewhat mitigated by cars equipped with Electronic Stability Control). Stepping on the brake — such as to disengage the cruise control — could result in the driver losing control of the vehicle.