cruise control system
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15-10-2009, 01:15 PM
Cruise control (speed control or auto cruise) is a system that automatically controls the speed of a motor vehicle. The system takes over the throttle of the car to maintain a steady speed as set by the driver
Theory of operation
In modern designs, the cruise control may need to be turned on before use â€ in some designs it is always "on" but not always enabled, others have a separate "on/off" switch, while still others just have an "on" switch that must be pressed after the vehicle has been started. Most designs have buttons for "set", "resume", "accelerate", and "coast" functions. Some also have a "cancel" button. Alternatively, tapping the brake or clutch pedal will disable the system so the driver can change the speed without resistance from the system. The system is operated with controls easily within the driver's reach, usually with two or more buttons on the steering wheel spokes or on the edge of the hub like those on Honda vehicles, on the turn signal stalk like in some General Motors vehicles or on a dedicated stalk like those found in Toyota and Mercedes-Benz vehicles. Early designs used a dial to set speed choice.
The driver must bring the car up to speed manually and use a button to set the cruise control to the current speed. The cruise control takes its speed signal from a rotating drive shaft, speedometer cable, wheel speed sensor or from the engine's RPM. Most systems do not allow the use of the cruise control below a certain speed (normally 35 mph/55 km/h) to discourage use in city driving. The car will maintain that speed by pulling the throttle cable with a solenoid or a vacuum driven servomechanism.
All systems must be turned off both explicitly and automatically, when the driver hits the brake or clutch. Cruise control often includes a memory feature to resume the set speed after braking and a coast feature to reset the speed lower without braking. When the cruise control is in effect, the throttle can still be used to accelerate the car, but once the accelerator is released the car will then slow down until it reaches the previously set speed.
On the latest vehicles fitted with electronic throttle control, cruise control can be easily integrated into the vehicle's engine management system. Cruise controls currently being developed include the ability to automatically reduce speed when the distance to a car in front, or the speed limit decreases. This is an advantage for those driving in unfamiliar areas.
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08-03-2011, 12:42 PM
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cruise control @2003.ppt (Size: 1.69 MB / Downloads: 260)
CRUISE CONTROL SYSTEMS
Cruise control is a new technological development which incorporates a factor of comfort in driving. Safety is only a small benefit of this system. In short, cruise control can be said to be a system which uses the principles of radar to determine the distances between two consecutive moving vehicles in which either one or both of them is incorporated with this system.
• Every minute, on average, at least one person dies in a crash.
• Air bags and seat belts save tens of thousands of people a year.
• But the ultimate solution and the only thing that will save far more lives, limbs and money is ? till 1958.
• Cruise control was commercially introduced in 1958 as an option on the Chrysler Imperial.
WHAT IS CRUISE CONTROL?
• Cruise control is a system, which automatically controls the speed of an automobile.
• Most cruise control systems don’t allow the use of cruise control below a certain speed.
• Blind inventor and mechanical engineer Ralph teetor invented cruise control in 1945.
• The basic operation of a cruise controller is to sense the speed of the vehicle, compare this speed to a desired reference, and then accelerate or decelerate the car as required.
• A simple control algorithm for controlling the speed is to use a "proportional plus integral" feedback.
• The performance of the system is robust with respect to it’s mass uncertainty.
HOW TO SET CRUISE CONTROL ?
• On &off
ADAPTIVE CRUISE CONTROL
• Adaptive Cruise Control (ACC) is an automotive feature that allows a vehicle's cruise control system to adapt the vehicle's speed to the traffic environment.
• In May 1998, Toyota became the first to introduce an ACC system on a production vehicle,luxury sedan.
• ACC systems detect the vehicle ahead through the use of either radar or lidar(light detecting and ranging).
• Lidar based ACCsystems are limited due to their poor working in bad whether.
PARTS AND WORKING
The main components of a typical radar-based ACC system are
• Fusion sensor
• Headway control unit
• Dashboard display
Fusion sensor: It is a combination of sensors and processors. They are
• Millimeter-wave radar
• Stereo camera
• Image processor
• Fusion processor
• Millimeter wave radar: It is a sensor which uses millimeter wave for detecting the position and velocity of a distant object.
• Range is calculated using the formula
C = 2*R/T
Where ‘C’ is the velocity of light
‘R’ is the range
‘T’ is the time of flight of transmission.
• Stereo camera: The camera’s function is detection of cars and other objects in the roadway.
• Image processor: It processes the images from the stereo camera and the data fed into the fusion processor.
• Fusion processor: The function of fusion processor is Data Fusion.
Headway control unit: It has control on the brakes and throttle and uses dashboard for immediate warnings.
Canceling Cruise Control Operation:
• Brake pedal is pressed
• 'Off' button is pressed
• Vehicle Speed < 25 mph
• An ACC system fault is detected
DANGERS OF CRUISE CONTROL
• It’s use on wet and slippery roads may cause serious problems.
• CACC(co-operative adaptive cruise control) tested in California.
• At 100 km/hr, that would amount to a distance between cars of less than 14 meters (roughly two car lengths).
• Fujitsu Ten has demonstrated a prototype system for so called called stop-and-go adaptive cruise control.
• Fully autonomous car is probably not viable in the foreseen future.
• Near by vehicles would be in constant communication with each other and act co-operatively.
• It will probably take decades, but car accidents may eventually become almost as rare as plane crashes are now.
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cruise control devices.ppt (Size: 2.3 MB / Downloads: 132)
Cruise control device first appeared in 1970 in USA
Assisting drivers in longitudinal vehicle control
Adaptive cruise control (ACC) developed as new generation
Cruise control is a system that automatically controls the speed of a motor vehicle.
Also known as speed control or auto cruise.
Adjusting the throttle position to maintain a speed set by the driver.
Uses the principle of radar to determine the distance between two consecutive moving vehicle.
The electromagnetic rays from radar system are sensed by sensors.
Advanced innovation in automotive technology.
Luxury vehicles offer ACC. Mercedes Benz first offer ACC.
Distance sensor is used.
The set distance (timed in seconds) is the desired distance between the ACC vehicle and the forward vehicle.
The set speed is the desired maximum speed to be regulated by the ACC system on an open road. If no forward vehicle is detected, the set speed is regulated.
PRINCIPLES OF ACC
Works by detecting the distance and speed of the vehicle using lidar or radar system
Speed is measured by Doppler effect
Second generation of ACC is stop and go cruise control (SACC)
ACC is control is a radar-based system that can monitor the vehicle in from (upto 600 feet) and adjust the speed of the vehicle to keep it at a pre-set distance behind the lead vehicle, even in most fog and rain conditions.
The system measures distance as a function of speed and can monitor the traffic
When the danger of a collision is detected, it provides a red warning light that flashes on the windshield.
The system provides an audible alert when it senses a reduction in traffic speed in vehicles ahead.
LIDAR is Light Detection And Ranging.
A laser diode was used to generate the light signal.
Beat frequency difference between a Frequency Modulated Continuous light Wave and its reflection is used as the control signal.
RADAR is Radio Detection And Ranging
It is operated by radiating energy into space and detecting the echo signal reflected from target
The currently used ‘Pulse Doppler RADAR’ uses the principle of ‘Doppler effect’ in determining the velocity of the target.
PULSE DOPPLER RADAR
PULSE DOPPLER RADAR
Wave oscillator produces the signal to be transmitted
Duplexer is a switching device
Doppler filter removes the noise
RADAR ANTENNA SCHEMES
Mechanically steered antenna
Electronically steered antenna
MECHANICALLY STEERED ANTENNA
ELECTRONICALLY STEERED ANTENNA
Phased array is a directive antenna made up of a number of individual antenna or radiating element
Radiation pattern is determined by the amplitude and phase of the current at each of its element
While RADAR target is the car’s rear spoiler the stereo camera is constantly captures all objects in its field of view.
It includes millimeter wave radar linked to a 640x480 pixel stereo camera
Car with fusion sensor arrangement
Sensing and controlling process
MILLIMETER WAVE RADAR
Millimeter-wave radar is a method used for detecting the position and velocity of a distant object.
Every 60 milliseconds, the sensor sends out a trio of overlapping beams of electromagnetic radiations
Range is calculated using the formula
The camera’s function is the same, as that of the radar, detection of cars and other objects in the roadway. Camera view reaches to a distance of 60 meters ahead of the vehicle. The stereo camera is situated by the rear view mirror.
The image-processing unit processes the images from the stereo camera and the data is then fed into the fusion processor
The function of fusion processor is termed as Data Fusion. Data fusion is a collection of techniques for combining the measurements from more than one sensor to provide a more unified result.
ADVANTAGES OF ACC
The driver is relieved from the task of careful acceleration, deceleration and braking in congested traffics.
A highly responsive traffic system adjusts itself to avoid accidents.
Fuel efficiency of the vehicle is increased
A cheap version is not yet realized.
A high market penetration is required if a society of intelligent vehicles is to be formed.
Encourages the driver to become careless.
The ACC systems not respond directly to the traffic signals.
Co-Cooperative Adaptive cruise control or CACC is already being tested in California .
ACC respond to the distance and speed of the car ahead ,CACC communicate with two or more cars and work together to avoid collision.
Communication is quicker, reliable and responsive.
The accidents caused by automobiles are goes on increasing.
The safety measures starting from air bags and seat belts have now reached to ACC and CACC systems.
By the invention of 360° sensors, car accidents may be as rare as plane accidents.
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Automatic Cruise Control
Automatic Cruise.ppt (Size: 1.59 MB / Downloads: 20)
Everyday the media brings us the horrible news on road accidents. Once a report said that the damaged property and other costs may equal 3 % of the world’s gross domestic product.
What Is Cruise Control?
Cruise Control is a system which is capable of maintaining the speed of a car at a desired level.
What Is Adaptive Cruise Control Systems?
Adaptive Cruise Control (ACC) technology automatically adjust the vehicle speed and distance to that of a target vehicle.
LIDAR (Light Detection and Ranging)
Lidar is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant target. The prevalent method to determine distance to an object or surface is to use laser pulses. Like the similar radar technology, which uses radio waves instead of light, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal. LIDAR The first acc system introduced by Toyota used
this method. By measuring the beat frequency difference between a Frequency Modulated Continuous light Wave (FMCW) and its reflection.
RADAR (Radio Detection and Ranging):
RADAR is an electromagnetic system for the detection and location of reflecting objects like air crafts, ships, space crafts or vehicles. It is operated by radiating energy into space and detecting the echo signal reflected from an object (target) the reflected energy is not only indicative of the presence but on comparison with the transmitted signal, other information of the target can be obtained. The currently used ‘Pulse
Doppler RADAR’ uses the principle of ‘Doppler effect’ in determining the velocity of the target.