Adaptive Cruise Control Report

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Transcript of Adaptive Cruise Control Report

Adaptive Cruise Control

TABLE OF CONTENTS1)

INTRODUCTION PRI NCIPLE WORKING

3 4 4 6 7 7 8 9 10 12 14 16 16 17 18 18 19 20

2) CRUISE CONTROL i. ii.

3) ADAPTIVE CRUISE CONTROL i. ii. iii. iv. v. vi. vii. viii. ix. x. xi.

OVERVIEW WHY ADAPTIVE CRUISE CONTROL COMPONENTS OF ADAPTIVE CRUISE CONTROL WORKING TYPES APPLICATIONS FEATURES OF ADAPTIVE CRUISE CONTROL COLLISION REPAIRS CAUTION ADVANTAGES LIMITATIONS

4) CONCLUSION 5) REFERENCE

1 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise Control

LIST OF FIGURESFIGURE 1 - CRUISE CONTROL LEVER FIGURE 2 - CRUISE CONTROL WORKING SYSTEM FIGURE 3 - WITHOUT ACC FIGURE 4 - ACC BUTTONS ON STEERING WHEEL FIGURE 5 - COMPONENTS OF ACC FIGURE 6 - CONCEPT OF ACC FIGURE 7 - WITH ACC FIGURE 8 - LASER BASED SENSOR FIGURE 9 - RADAR BASED SENSOR FIGURE 10 - DISPLAY OF DISTRONIC SYSTEM FIGURE 11 - DISPLAY OF DISTRONIC SYSTEM 4 6 7 7 9 10 12 12 13 15 15

2 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise Control

INTRODUCTIONMentally, driving is a highly demanding activity - a driver must maintain a high level of concentration for long periods and be ready to react within a split second to changing situations. In particular, drivers must constantly assess the distance and relative speed of vehicles in front and adjust their own speed accordingly. Those tasks can now be performed by Adaptive Cruise Control (ACC) system, which is an extension of the conventional cruise control system. Like a conventional cruise control system, ACC keeps the vehicle at a set constant speed. The significant difference, however, is that if a car with ACC is confronted with a slower moving vehicle ahead, it is automatically slowed down and then follows the slower vehicle at a set distance. Once the road ahead is clear again, the ACC accelerates the car back to the previous set cruising speed. In that way, ACC integrates a vehicle harmoniously into the traffic flow.

3 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise Control

CRUISE CONTROLCruise Control is a system which is capable of maintaining the speed of a car at a desired level. The conventional the basic systems are capable of taking over the throttle once the driver activates Cruise Control and sets the desired speed. In most of the cars, the cruise control buttons are mounted on the steering wheel, just like the audio control buttons, whereas in older car models a separate lever is provided similar to the ones used for windscreen wipers and headlights. The basic ones are often equipped with four buttons: on, off, resume and coast whereas the newer current systems are offered with one or two controls only but are way too convenient. Once enabled the new ones only ask the driver to set the maximum and minimum cruising speeds after which it takes over the controls and the same gets disabled as soon as the driver presses the throttle, brake or clutch pedal. This feature is very useful for long drives where the roads are fairly good and high speed cruising is possible. The driver can set the cars cruise control system close to the speed limit of the road and just relax with his foot off from the accelerator and brakes, the car will maintain the speed set on the cruise control system using the arrangements (cars computers, activators etc.) which are provided in the car.

PRINCIPLE

Figure 1: Cruise control lever

4 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise ControlThe cruise control system actually has a lot of functions other than controlling the speed of your car. For instance, the cruise control pictured below 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 -- the cruise control will disengage as soon as you hit the brake pedal, and it won't engage at speeds less than 25 mph (40 kph).

The system pictured below has five buttons: On, Off, Set/Accel, 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.

The on and off buttons don't actually do much. Hitting the on button does not do anything except tell the car that you might be hitting another button soon. The off button turns the cruise control off even if it is engaged. Some cruise controls don't have these buttons; instead, they turn off when the driver hits the brakes, and turn on when the driver hits the set button.

The set/accel button tells the car to maintain the speed you are currently driving. If you hit the set button at 45 mph, the car will maintain your speed at 45 mph. Holding down the set/accel button will make the car accelerate; and on this car, tapping it once will make the car go 1 mph faster.

If you recently disengaged the cruise control by hitting the brake pedal, hitting the resume button will command the car to accelerate back to the most recent speed setting.

Holding down the coast button will cause the car to decelerate, just as if you took your foot completely off the gas. On this car, tapping the coast button once will cause the car to slow down by 1 mph.

The brake pedal and clutch pedal each have a switch that disengages the cruise control as soon as the pedal is pressed, so you can shut off the cruise control with a light tap on the brake or clutch.

5 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise Control

WORKING

Figure 2: Cruise control working system

The modern systems constitute of a computer control system, several inputs signals, vacuum actuator and throttle position sensor. The main computers takes the input from the starring wheel controls, vehicle speed signals etc. and sends these to a vacuum actuator through a vacuum valve. The actuator in turn is connected to the throttle valve by a cable and the throttle valve has a position sensor mounted on it. The sensor directs the signals back to the main computer, so it forms a loop. Signals are sent from the computer to the actuator which further positions the throttle through a cable. The position of the throttle is sensed and the signals are sent back to the computer thereby ensuring that the correct position for the set speed has been reached and if it is not there, the computer again positions the throttle.

6 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise Control

ADAPTIVE CRUISE CONTROL

OVERVIEWACC is an extension of conventional cruise control systems. An ACC system is a driver convenience feature designed to maintain a set following distance from the vehicle ahead. ACC is not a collision warning or avoidance system. An ACC system is designed to assist the driver and is not a fully independent driving system. As with conventional cruise control systems, manual inputs from the driver, both to the accelerator and brake, take priority over the ACC system. Cruise control systems may also be known as speed control systems.

Figure 3: Without ACC

An ACC system uses a distance sensor that projects a beam forward to detect a vehicle ahead.

7 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise ControlFigure 4: ACC buttons on BMW steering wheel

WHY ADAPTIVE CRUISE CONTROLComfortable distance to the car ahead increases driving safety and ensures a more relaxed driving experience. Adaptive Cruise Control ensures that there is enough distance to the car ahead, even if it unexpectedly lowers the speed. With Adaptive Cruise Control we have enhanced the conventional systems for speed control to a driver assistant with an added value. The system makes it possible to adapt the distance to the car ahead without the drivers intervention, effectively relieving the driver. Highway and rural road drives are more relaxed and traffic flows better altogether, since acceleration and braking maneuvers are automatically adjusted. 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 77-GHz Autocruise radar system made by TRW has a forward-looking range of up to 492 feet (150 meters), and operates at vehicle speeds ranging from 18.6 miles per hour (30 kph) to 111 mph (180 kph). Delphi's 76-GHz system can also detect objects as far away as 492 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. These systems are being enhanced to include collision warning capabilities

8 Department of Mechanical Engineering | VVCE, Mysore

Adaptive Cruise Controlthat will warn drivers through visual and/or audio signals that a collision is imminent and that braking or evasive steering is needed. Adaptive Cruise Control (ACC) technology improves upon the function of standard cruise control by automatically adj