adaptive cruise control full report
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.doc   ADAPTIVE CRUISE CONTROL ACC full report.doc (Size: 582 KB / Downloads: 810)
ABSTRACT
The concept of assisting driver in the task of longitudinal vehicle control is known as cruise control. Starting from the cruise control devices of the seventies and eighties, now the technology has reached cooperative adaptive cruise control. This paper will address the basic concept of adaptive cruise control and the requirement to realize its improved versions including stop and go adaptive cruise control and cooperative adaptive cruise control. The conventional cruise control was capable only to maintain a set speed by accelerating or decelerating the vehicle. Adaptive cruise control devices are capable of assisting the driver to keep a safe distance from the preceding vehicle by controlling the engine throttle and brake according to the sensor data about the vehicle. Most of the systems use RADAR as the sensor .a few use LIDAR also. Controller includes the digital signal processing modules and microcontroller chips specially designed for actuating throttle and brake. The stop and go cruise control is for the slow and congested traffic of the cities where the traffic may be frequently stopped. Cooperative controllers are not yet released but postulations are already there. This paper includes a brief theory of pulse Doppler radar and FM-CW LIDAR used as sensors and the basic concept of the controller.

1. INTRODUCTION
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 worldâ„¢s gross domestic product. The concept of assisting driver in longitudinal vehicle control to avoid collisions has been a major focal point of research at many automobile companies and research organizations. The idea of driver assistance was started with the Ëœcruise control devicesâ„¢ first appeared in 1970â„¢s in USA. When switched on, this device takes up the task of the task of accelerating or braking to maintain a constant speed. But it could not consider the other vehicles on the road.
An ËœAdaptive Cruise Controlâ„¢ (ACC) system developed as the next generation assisted the driver to keep a safe distance from the vehicle in front. This system is now available only in some luxury cars like Mercedes S-class, Jaguar and Volvo trucks the U.S. Department of transportation and Japanâ„¢s ACAHSR have started developing ËœIntelligent Vehiclesâ„¢ that can communicate with each other with the help of a system called ËœCo operative Adaptive Cruise Controlâ„¢ .this paper addresses the concept of Adaptive Cruise Control and its improved versions.

2. ADAPTIVE CRUISE CONTROL (ACC)
2.1 PRINCIPLE OF ACC
ACC works by detecting the distance and speed of the vehicles ahead by using either a Lidar system or a Radar system [1, 2].The time taken by the transmission and reception is the key of the distance measurement while the shift in frequency of the reflected beam by Doppler Effect is measured to know the speed. According to this, the brake and throttle controls are done to keep the vehicle in a safe position with respect to the other. These systems are characterized by a moderately low level of brake and throttle authority. These are predominantly designed for highway applications with rather homogenous traffic behavior. The second generation of ACC is the Stop and Go Cruise Control (SACC) [2] whose objective is to offer the customer longitudinal support on cruise control at lower speeds down to zero velocity [3]. The SACC can help a driver in situations where all lanes are occupied by vehicles or where it is not possible to set a constant speed or in a frequently stopped and congested traffic [2]. There is a clear distinction between ACC and SACC with respect to stationary targets. The ACC philosophy is that it will be operated in well structured roads with an orderly traffic flow with speed of vehicles around 40km/hour [3]. While SACC system should be able to deal with stationary targets because within its area of operation the system will encounter such objects very frequently.
2.2 CONSTITUENTS OF AN ACC SYSTEM:
1. A sensor (LIDAR or RADAR) usually kept behind the grill of the vehicle to obtain the information regarding the vehicle ahead. The relevant target data may be velocity, distance, angular position and lateral acceleration.
2. Longitudinal controller which receives the sensor data and process it to generate the commands to the actuators of brakes throttle or gear box using Control Area Network (CAN) of the vehicle.
3. SENSOR OPTIONS:
Currently four means of object detection are technically feasible and applicable in a vehicle environment [2]. They are
1. RADAR
2. LIDAR
3. VISION SENSORS
4. ULTRASONIC SENSOR
The first ACC system used LIDAR sensor.

3.1 LIDAR (Light Detection and Ranging)
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 [3].

Fig 1.Range estimation using FMCW-LIDAR
A company named Vorad Technologies has developed a system which measured up to one hundred meters. A low powered, high frequency modulated laser diode was used to generate the light signal.
Most of the current acc systems are based on 77GHz RADAR sensors. The RADAR systems have the great advantage that the relative velocity can be measured directly, and the performance is not affected by heavy rain and fog. LIDAR system is of low cost and provides good angular resolution although these weather conditions restrict its use within a 30 to 40 meters range.
3.2 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 ËœPulse Doppler RADARâ„¢ uses the principle of ËœDoppler effectâ„¢ in determining the velocity of the target [5].
3.2.1 PULSE DOPPLER RADAR:
The block diagram of pulse Doppler radar is as shown in figure.2.
The continuous wave oscillator produces the signal to be transmitted and it is pulse modulated and power amplified. The Ëœduplexerâ„¢ is a switching device which is fast-acting to switch the single antenna from transmitter to receiver and back. The duplexer is a gas-discharge device called TR-switch. The high power pulse from transmitter causes the device to breakdown and to protect the receiver. On reception, duplexer directs the echo signal to the receiver. The detector demodulates the received signal and the Doppler filter removes the noise and outputs the frequency shift Ëœfdâ„¢.

Fig2. Block diagram of pulse Doppler radar

3.2.2 EFFECT OF DOPPLER SHIFT:
The transmitter generates a continuous sinusoidal oscillation at frequency Ëœftâ„¢which is then radiated by the antenna. On reflection by a moving object, the transmitted signal is shifted by the Doppler Effect by Ëœfdâ„¢.
If the range to the target is ˜R™, total number of wavelength is ˜™ in the two way- path is given by,
n = 2R/
The phase change corresponding to each =2p
So total phase change, p=2n
=2(2R/ ) p
So, if target moves, ËœRâ„¢ changes and hence Ëœfâ„¢ also changes.
Now, the rate of change of phase, or the Ëœangular frequencyâ„¢ is
W=df/dt =4 p (df/dt)/
Let Vr be the linear velocity, called as Ëœradial velocityâ„¢
Wd = 4 pVr/ =2pfd.
Fd=2Vr /
But = ft, the transmitted velocity.
Fd= (2c Vr)/ ft
So by measuring the shift, Vr is found. The Ëœplusâ„¢ sign indicates that the target and the transmitter are closing in. i.e. if the target is near, the echoed signal will have larger frequency.
3.2.3 RADAR ANTENNA SCHEMES:
Radar systems employ a variety of sensing and processing methods to determine the position and speed of vehicles ahead. Two such important schemes are:
1. mechanically steered antenna
2. electronically steered antenna
1. Mechanically steered antenna:

A parabolic reflector is used as mechanically steered antenna. The parabolic surface is illuminated by the source of energy placed at the focus of the parabola. Rotating about its axis, a circular parabola is formed. A symmetrical beam can be thus obtained. The rays originating from focus are reflected parallel to the axis of parabola. [fig (3).]

Fig 3.Parabolic reflector antenna
2. Electronically steered phased array radar antenna
A phased array is a directive antenna made up of a number of individual antennas, or radiating elements. The radiation pattern is determined by the amplitude and phase of current at each of its elements. It has the advantage of being able to have its beam electronically steered in angles by changing phase of current at each element. The beam of a large fixed phased array antenna is therefore can be rapidly steered from one direction to another without mechanical positioning [1, 5].
Consider the following figure with ˜N elements placed (equally separated) with a distance˜d™ apart. Suppose they have uniform response to signals from all directions. Element ˜1™ is taken as reference with zero phase.


Fig 4. Phased array elements (example: reception of the beams)
From simple geometry, we can get difference between path lengths of beam1 and that of beam2 is x = d sin, where ˜™ is the angle of incidence of the beams. This gives phase difference between adjacent elements as F= 2p (d sin)/ , where ˜™ is the wave length of the signal. But if the current through a ferro electric element is changed, the dielectric constant ˜e™ is changed since electron density is changed, and for an electromagnetic radiation, F = 2px /
=2pxf/v,
here the velocity v = f = 1/ (vµ e)
Hence F=2pxf (vµ e).

So if Ëœeâ„¢ is changed ËœFâ„¢ also changes and inserting ËœNâ„¢ phase shifting elements to steer the beam, we can obtain an electronically steered beam.
Regardless of the scanning mechanism the radars typically operate in the millimeter wave region at 76-77 GHz.
The system should be mounted inside the front grille of the car as shown in figure (5). So its size is to be small. A typical radar produced by Delphi-Delco Electronic systems is having the size of two stacked paper back books(14x7x10 cm)[1].
3.3 FUSION SENSOR
The new sensor system introduced by Fujitsu Ten Ltd. and Honda through their PATH program includes millimeter wave radar linked to a 640x480 pixel stereo camera with a 40 degree viewing angle. These two parts work together to track the car from the non-moving objects. While RADAR target is the carâ„¢s rear bumper, the stereo camera is constantly captures all objects in its field of view.

Fig5. A prototype of a car with fusion sensor arrangement

Fig 6.Block diagram of sensing and controlling process
The image processor measures the distances to the objects through triangulation method. This method includes an algorithm based on the detection of the vertical edges and distance. Incorporating both the 16-degree field of view of radar and 40-degree field of view of camera enhances the performance in tight curves [4].
4. SPACE OF MANEUVERABILITY AND STOPPING DISTANCE
The space of maneuverability is the space required by the driver to maneuver a vehicle. An average driver uses larger sideways acceleration while vehicle speed is low. If the curve radius of a possible trajectory is Ëœrâ„¢ for a given velocity Ëœvâ„¢ and sideways acceleration Ëœayâ„¢ ,then r= / ay [2].so to get the required Ëœrâ„¢ ,when Ëœvâ„¢ is low, Ëœayâ„¢ is also to be low correspondingly. The stopping distance is given by, Ds = .5 u /ax + td u, where Ëœuâ„¢ is the initial speed Ëœtdâ„¢ is the time taken by the system to receive and process the sensor data and Ëœaxâ„¢ is the acceleration of the vehicle .the figure shows the detection of edges of the preceding vehicles.

Fig 7.Detection of vehicle edges by the fusion sensor
5. CONTROLLER
The controller translates the situation into appropriate actions through brake and pedal and throttle control actions.
Depending on the present traffic situation, two types of controls are possible.
1. Speed control
2. Headway control
If there is no vehicle presently in front, then the speed is controlled about a set point just as in conventional cruise control. But in order to keep a safe distance between the vehicle s, the headway control is required.
5.1ARTIFICIAL COGNITION
The conversion of raw information from sensors to control actions by the two steps:-
1. Analyzing the traffic conditions
2. Deciding on a particular situation
The controller translates the desired situation into appropriate control action through brake and throttle actuation.[2]. The controller concept is simplified in the flow-diagram:

Fig 8.Flow diagram of controlling process
5.2. EXAMPLE OF ADAPTIVE CRUISE CONTROLLER (MOTOROLA ACC)

The Motorola ACC constitutes a DSP module having MGT5200 which provides a multiply-accumulator. The sensor data such as Radar information, that from camera and an IR sensor are processed in it, to generate the input data for the controller modules like HC12 and MPC565.[6].

Fig9. Motorola ACC
5.2.1 MPC565
It is a throttle controller or an engine speed controller. It consists of the following features
1. SRAM (1MB to10 MB)
2. FLASH 1MB
3. EEPROM (4KB to 32 KB)
4. Real time clock
5. 4 x UART interfaces
6. 3 X CAN interfaces
7. 64-bit floating point unit.
The MPC 565 can be programmed to generate the control signals according to the sensor data. ËœThe Phycore-MPC 565 developersâ„¢ are available to program and develop the desired controller.
The throttle valve is actuated and the air intake is controlled so the requirement of fuel for the right proportion with the air also increases. So more fuel is injected and engine speed is changed.
5.2.2 HC12
The HC12 is a breaking controller which receives data from the wheel speed sensors and from the DSP module. It generates the braking control signal.
5.2.3 CAN (Control Area Network) BUS
CAN BUS is the network established between microcontrollers. It is a2-wire, half-duplex, high speed network for high speed high speed applications with short messages. It can theoretically link up to 2032 devices on a network. But today the practical limit is 110 devices. It offers high speed communication rate up to 1Mbits per second and allows real time control. [7].
Each module in the ACC connected to the CAN is called Ëœa nodeâ„¢. All are acting as transceivers. The CAN bus carries data to and from all nodes and provides quicker control transfer to each module.
The actuator used for throttle control is a solenoid actuator. The signal through the coil can push or pull the plunger.
6. CO OPERATIVE ADAPTIVE CRUISE CONTROL [CACC]
Though conventional ACC and SACC are still expensive novelties, the next generation called Cooperative ACC is already being tested. While ACC can respond to the difference between its own behavior and that of the preceding vehicle, the CACC system allows the vehicles to communicate and to work together to avoid collision.[2,4].
Partners of Advanced Transit Highways (PATH) “a program of California Department of Transportation and University of California with companies like Honda conducted an experiment in which three test vehicles used a communication protocol in which the lead car can broadcast information about its speed, acceleration ,breaking capacity to the rest of the groups in every 20ms.
PATH is dedicated to develop systems that allow cars to set up platoons of vehicles in which the cars communicate with each other by exchanging signals using protocols like Bluetooth.
6.1. MAIN POSTULATIONS ABOUT CACC:

1. In CACC mode, the preceding vehicles can communicate actively with the following vehicles so that their speed can be coordinated with each other.
2. Because communication is quicker, more reliable and responsive compared to autonomous sensing as in ACC.
3. Because braking rates, breaking capacity and other important information about the vehicles can be exchanged, safer and closer vehicle traffic is possible.
Fig 10.Under CACC, both the leading and following vehicles are electronically tied to a virtual reference vehicle, as well as to each other.
7. ADVANTAGES
1. The driver is relieved from the task of careful acceleration, deceleration and braking in congested traffics.
2. A highly responsive traffic system that adjusts itself to avoid accidents can be developed.
3. Since the breaking and acceleration are done in a systematic way, the fuel efficiency of the vehicle is increased.
DISADVANTAGES
1. A cheap version is not yet realized.
2. A high market penetration is required if a society of intelligent vehicles is to be formed.
3. Encourages the driver to become careless. It can lead to severe accidents if the system is malfunctioning.
4. The ACC systems yet evolved enable vehicles to cooperate with the other vehicles and hence do not respond directly to the traffic signals.
8. CONCLUSION
The accidents caused by automobiles are injuring lakhs of people every year. The safety measures starting from air bags and seat belts have now reached to ACC, SACC and CACC systems. The researchers of Intelligent Vehicles Initiative in USA and the Ertico program of Europe are working on technologies that may ultimately lead to vehicles that are wrapped in a cocoon of sensors with a 360 “degree view of their surroundings. It will probably take decades, but car accidents may eventually become as rare as plane accidents are now, even though the road laws will have to be changed, upto an extent since the non-human part of the vehicle controlling will become predominant.
9. REFERENCES
1. Willie D. Jones, Keeping cars from crashing. , IEEE Spectrum September 2001.
2. P.Venhovens, K. Naab and B. Adiprasto, Stop And Go Cruise Control, International Journal of Automotive Technology, Vol.1, No.2, 2000.
3. Martin D. Adams, Co axial range Measurement-Current trends for Mobile robotic Applications, IEEE Sensors journal, Vol.2, no.1 Feb.2002.
4. path.Berkeley.edu
5. Merril I.Skolnik, Introduction To RADAR Systems.Tata Mc Grawhill edition 2001.
6. motorola /semiconductor.com
7. computer-solutions.co.uk


CONTENTS
1. INTRODUCTION
2. PRINCIPLE OF ACC
2.1 PRINCIPLE OF ACC
2.2 CONSTITUENTS OF AN ACC SYSTEM
3. SENSOR OPTIONS
3.1 LIDAR
3.2 RADAR
3.2.1 PULSE DOPPLER RADAR
3.2.2 EFFECT OF DOPPLER SHIFT
3.2.3 RADAR ANTENNA SCHEMES
3.3 FUSION SENSOR
4. SPACE OF MANEUVERABILITY AND STOPPING DISTANCE:
5. CONTROLLER
5.1ARTIFICIAL COGNITION
5.2. EXAMPLE OF ADAPTIVE CRUISE CONTROLLER
6. CO OPERATIVE ADAPTIVE CRUISE CONTROL [CACC]
6.1. MAIN POSTULATIONS ABOUT CACC
7. ADVANTAGES AND DISADVANTAGES
8. CONCLUSION
9. REFERENCES

ACKNOWLEDGEMENT
I extend my sincere gratitude towards Prof. Head of Department for giving us his invaluable knowledge and wonderful technical guidance
I express my thanks to Mr. our group tutor and also to our staff advisor Ms and Mr for their kind
co-operation and guidance for preparing and presenting this seminar and presentation.
I also thank all the other faculty members of department and my friends for their help and support.
Use Search at http://topicideas.net/search.php wisely To Get Information About Project Topic and Seminar ideas with report/source code along pdf and ppt presenaion
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ABSTRACT
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. A radar system attached to the front of the vehicle is used to detect whether slower moving vehicles are in the ACC vehicle's path. If a slower moving vehicle is detected, the ACC system will slow the vehicle down and control the clearance, or time gap, between the ACC vehicle and the forward vehicle. If the system detects that the forward vehicle is no longer in the ACC vehicle's path, the ACC system will accelerate the vehicle back to its set cruise control speed. This operation allows the ACC vehicle to autonomously slow down and speed up with traffic without intervention from the driver. The method by which the ACC vehicle's speed is controlled is via engine throttle control and limited brake operation.

The system can be enhanced to support the following applications namely Pedestrian protection, Lane Departure Warning and Lane keeping, Fusion with Radar and Lidar sensors, Stop and Go ACC, Collision mitigation, Automatic headlamps activation, Intelligent high beam control.
CONTENTS
Introduction
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. A radar system attached to the front of the vehicle is used to detect whether slower moving vehicles are in the ACC vehicle's path. If a slower moving vehicle is detected, the ACC system will slow the vehicle down and control the clearance, or time gap, between the ACC vehicle and the forward vehicle. If the system detects that the forward vehicle is no longer in the ACC vehicle's path, the ACC system will accelerate the vehicle back to its set cruise control speed. This operation allows the ACC vehicle to autonomously slow down and speed up with traffic without intervention from the driver. The method by which the ACC vehicle's speed is controlled is via engine throttle control and limited brake operation.
Physical Overview
Definitions
Adaptive Cruise Control (ACC) “ An enhancement to a conventional cruise control system which allows the ACC vehicle to follow a forward vehicle at an appropriate distance.
ACC vehicle “ the subject vehicle equipped with the ACC system.
Active brake control “ a function which causes application of the brakes without driver application of the brake pedal.
Clearance “ distance from the forward vehicle's trailing surface to the ACC vehicle's leading surface.
Forward vehicle “ any one of the vehicles in front of and moving in the same direction and traveling on the same roadway as the ACC vehicle.
Set speed “ the desired cruise control travel speed set by the driver and is the maximum desired speed of the vehicle while under ACC control.
System states
ACC off state “ direct access to the 'ACC active' state is disabled.
ACC standby state “ system is ready for activation by the driver.
ACC active state “ the ACC system is in active control of the vehicle's speed.
ACC speed control state “ a substate of 'ACC active' state in which no forward vehicles are present such that the ACC system is controlling vehicle speed to the 'set speed' as is typical with conventional cruise control systems.
ACC time gap control state “ a substate of 'ACC active' state in which time gap, or headway, between the ACC vehicle and the target vehicle is being controlled.
Target vehicle “ one of the forward vehicles in the path of the ACC vehicle that is closest to the ACC vehicle.
Time gap “ the time interval between the ACC vehicle and the target vehicle. The 'time gap' is related to the 'clearance' and vehicle speed by:
time gap = clearance / ACC vehicle speed.
Physical Layout
The ACC system consists of a series of interconnecting components and systems. The method of communication between the different modules is via a serial communication network known as the Controller Area Network (CAN).
ACC Module “ The primary function of the ACC module is to process the radar information and determine if a forward vehicle is present. When the ACC system is in 'time gap control', it sends information to the Engine Control and Brake Control modules to control the clearance between the ACC Vehicle and the Target Vehicle.
Engine Control Module “ The primary function of the Engine Control Module is to receive information from the ACC module and Instrument Cluster and control the vehicle's speed based on this information. The Engine Control Module controls vehicle speed by controlling the engine's throttle.
Brake Control Module “ The primary function of the Brake Control Module is to determine vehicle speed via each wheel and to decelerate the vehicle by applying the brakes when requested by the ACC Module. The braking system is hydraulic with electronic enhancement, such as an ABS brake system, and is not full authority brake by wire.
Instrument Cluster “ The primary function of the Instrument Cluster is to process the Cruise Switches and send their information to the ACC and Engine Control Modules. The Instrument Cluster also displays text messages and telltales for the driver so that the driver has information regarding the state of the ACC system.
CAN “ The Controller Area Network (CAN) is an automotive standard network that utilizes a 2 wire bus to transmit and receive data. Each node on the network has the capability to transmit 0 to 8 bytes of data in a message frame. A message frame consists of a message header, followed by 0 to 8 data bytes, and then a checksum. The message header is a unique identifier that determines the message priority. Any node on the network can transmit data if the bus is free. If multiple nodes attempt to transmit at the same time, an arbitration scheme is used to determine which node will control the bus. The message with the highest priority, as defined in its header, will win the arbitration and its message will be transmitted. The losing message will retry to send its message as soon as it detects a bus free state.
Cruise Switches “ The Cruise Switches are mounted on the steering wheel and have several buttons which allow the driver to command operation of the ACC system. The switches include:
'On': place system in the 'ACC standby' state
'Off'': cancel ACC operation and place system in the 'ACC off' state
'Set +': activate ACC and establish set speed or accelerate
'Coast': decelerate
'Resume': resume to set speed
'Time Gap +': increase gap
'Time gap “': decrease gap
Brake Switches “ There are two brake switches, Brake Switch 1 (BS1) and Brake Switch 2 (BS2). When either brake switch is activated, Cruise Control operation is deactivated and the system enters 'ACC standby' state.
Brake Lights “ When the Brake Control Module applies the brakes in response to an ACC request, it will illuminate the brake lights to warn vehicles behind the ACC vehicle that it is decelerating.
Operational Overview
The driver interface for the ACC system is very similar to a conventional cruise control system.The driver operates the system via a set of switches on
the steering wheel. The switches arethe same as for a conventional cruise control system except for the addition of two switches to control the time gap between the ACC vehicle and the target vehicle. In addition there are a series of text messages that can be displayed on the instrument cluster to inform the driver of the state of the ACC system and to provide any necessary warnings. The driver engages the ACC system by first pressing the ON switch which places the system into the 'ACC standby' state. The driver then presses the Set switch to enter the 'ACC active' state at which point the ACC system attempts to control the vehicle to the driver's set speed dependent upon the traffic environment.
Initialization
When the ignition key is in the off position, no power is applied to any of the systems. When the key is cycled to the on position, the ACC system initializes to the 'ACC off' state.
Engaging Cruise Control
Entering 'ACC standby' - Before active cruise control can be engaged the driver must first enter 'ACC standby'. This is performed by the driver pressing the ACC 'On' button. If no system faults are present, the ACC system will transition to the 'ACC standby' state.
Entering 'ACC active' “ The driver enters the 'ACC active' state by pressing the 'Set' or 'Resume' button. If a prior set speed is present in memory, the system uses this prior value as the target speed when Resume is pressed, else, the current speed of when the Set button was pressed will become the target speed. The following conditions must be true for the system to enter 'ACC active' in response to the cruise switches:
Brake Switch 1 = brake not applied
Brake Switch 2 = brake not applied
Vehicle Speed >= 25 mph
When entering active ACC control, the vehicle speed is controlled either to maintain a set speed or to maintain a time gap to a forward vehicle, whichever speed is lower.
Canceling Cruise Control Operation
Cruise Control operation may be canceled by the operator or automatically via the ACC system. Either of the following conditions will deactivate ACC:
Brake pedal is pressed
'Off' button is pressed
Vehicle Speed < 25 mph
An ACC system fault is detected
Operation In Speed Control Mode (ACC Speed Control)
Operation during this mode is equivalent to that of conventional speed control. If no forward vehicle is present within the Time Gap or clearance of the system, the vehicle's speed is maintained at the target speed. The engine control system controls the engine output via throttle control to maintain the vehicle speed at the target speed.
Operation In Follow Mode (ACC Time Gap Control)
The ACC system enters follow mode or 'ACC time gap control' if the radar detects a forward vehicle at or within the clearance distance. During this mode of operation, the ACC system sends a target speed to the Engine Control Module and deceleration commands to the Brake Control module to maintain the set time gap between the vehicles.
Deceleration control “ The ACC system decelerates the vehicle by lowering the target speed sent to the Engine Control Module and sending a brake deceleration command to the Brake Control Module. The maximum allowed braking effort of the system is 0.2 [g]. During brake deceleration events, the Brake Control Module activates the brake lights.
Acceleration control “ The ACC system accelerates the vehicle by increasing the target speed sent to the Engine Control Module. The Engine Control Module tries to maintain the target speed and can accelerate the vehicle at a rate of up to 0.2 [g] of acceleration.
Adjusting the time gap “ The driver can adjust the time gap via the 'Time Gap +' and 'Time Gap “' switches. Pressing the 'Time Gap +' switch causes the time gap value to increase and therefore the clearance between the two vehicles to increase. Pressing the 'Time Gap “' switch causes the time gap value to decrease and therefore the clearance between the two vehicles to decrease.
Reaction to a slow moving or stopped vehicle “ Situations may occur such that the ACC system is not able to maintain the time gap within the deceleration authority of the system, 0.2 [g]. The clearance between the ACC vehicle and the forward vehicle may be rapidly decreasing or the minimum vehicle speed of 25 [mph] may be reached. Under these situations the ACC system enters 'ACC standby' and alerts the driver by displaying a "Driver Intervention Required" text message on the instrument cluster and by turning on an audible chime. If the brakes were being applied by the ACC system, they will be slowly released. At this point the driver must take control of the vehicle.
Transitioning Between Speed Control and Follow Modes
The ACC system automatically transitions between Speed Control and Time Gap (Follow) Modes. The mode of operation is determined by the lower of the set speed for Speed Control Mode and the target speed to maintain the gap between the ACC vehicle and a forward vehicle. Basically, if no vehicle is present within the clearance distance, the system will operate in Speed Control mode, else, it will operate in Time Gap mode.
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ADAPTIVE CRUISE CONTROL
INTRODUCTION
Mentally, 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.
WHY ADAPTIVE CRUISE CONTROL?
Comfortable 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 driverâ„¢s 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.
ADAPTIVE CRUISE CONTROL
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 that 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 adjusting the vehicle speed and distance to that of a target vehicle. ACC uses a long range radar sensor to detect a target vehicle up to 200 meters in front and automatically adjusts the ACC vehicle speed and gap accordingly. ACC automatically decelerates or accelerates the vehicle according to the desired speed and distance settings established by the driver. As per standard cruise control the driver can override the system at any time.

Figure: THE CONCEPT OF ACC.
HOW DOES IT WORK?
The radar headway sensor sends information to a digital signal processor, which in turn translates the speed and distance information for a longitudinal controller. The result? 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 adaptive cruise control (ACC) system depends on two infrared sensors to detect cars up ahead. Each sensor has an emitter, which sends out a beam of infrared light energy, and a receiver, which captures light reflected back from the vehicle ahead.
The first sensor, called the sweep long-range sensor, uses a narrow infrared beam to detect objects six to 50 yards away. At its widest point, the beam covers no more than the width of one highway lane, so this sensor detects only vehicles directly ahead and doesn't detect cars in other lanes. Even so, it has to deal with some tricky situations, like keeping track of the right target when the car goes around a curve. To deal with that problem, the system has a solid-state gyro that instantaneously transmits curve-radius information to the sweep sensor, which steers its beam accordingly.
Another challenge arises when a car suddenly cuts in front of an ACC-equipped car. Because the sweep sensor's beam is so narrow, it doesn't "see" the other car until it's smack in the middle of the lane. That's where the other sensor, called the cut-in sensor, comes in. It has two wide beams that "look" into adjacent lanes, up to a distance of 30 yards ahead. And because it ignores anything that isn't moving at least 30 percent as fast as the car in which it is mounted, highway signs and parked cars on the side of the road don't confuse it.
Information from the sensors goes to the Vehicle Application Controller (VAC), the system's computing and communication center. The VAC reads the settings the driver has selected and figures out such things as how fast the car should go to maintain the proper distance from cars ahead and when the car should release the throttle or downshift to slow down. Then it communicates that information to devices that control the engine and the transmission.
There are several inputs:
System on/off: If on, denotes that the cruise-control system should maintain the car speed.
Engine on/off: If on, denotes that the car engine is turned on; the cruise-control system is only active if the engine is on.
Pulses from wheel: A pulse is sent for every revolution of the wheel.
Accelerator: Indication of how far the accelerator has been pressed.
Brake: On when the brake is pressed; the cruise-control system temporarily reverts to manual control if the brake is pressed.
Increase/Decrease Speed: Increase or decrease the maintained speed; only applicable if the cruise-control system is on.
Resume: Resume the last maintained speed; only applicable if the cruise-control system is on.
Clock: Timing pulse every millisecond.
There is one output from the system:
Throttle: Digital value for the engineer throttle setting.
ADAPTIVE CRUISE CONTROL FEATURES
o Maintains a safe, comfortable distance between vehicles without driver interventions
o Maintains a consistent performance in poor visibility conditions.
o Maintains a continuous performance during road turns and elevation changes
o Alerts drivers by way of automatic braking.
ADVANTAGES
Some of those advantages include:
¢ Its usefulness for long drives across 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. Such drivers should note, however, that a cruise control may go over its setting on a downhill which is steep enough to accelerate with an idling engine.
¢ Reduction in accident rate for vehicles fitted with collision avoidance type systems
¢ Reduction in driver fatigue
¢ Interconnection to more advanced future systems.
LIMITATIONS
One of the biggest challenges in designing ACC systems today are the costs associated with the robust system. Though current costs are substantial, they are slowly decreasing.
Auto manufacturers stress that advanced cruise control does not drive the car for you, and it's not meant to be used in heavy traffic. But, for long trips, it's a convenience that allows you to focus more on your driving.
CONCLUSIONS
Despite the introduction of the system to the market place, these are still early days. The current system can measure up to 150m ahead of the car and reduce the car's speed if an obstruction appears. What it can't do, at the moment, is bring the car to a halt.
Whatever happens, the ACC market looks set to explode. The project and implimentationed figures make startling reading. In 2002 there are no more than 100,000 vehicles fitted with ACC, but that figure is set to reach eight million in four years' time, with Europe, South-East Asia and the US accounting for about a third each. Around 17% of all European-built cars are likely to have ACC fitted as standard by then.
Expansion is bound to slow down thereafter, but by 2010 the global market will be 11.5 million units, representing an industry value of around $2.4 billion - and enormously more than that saved in repair bills, hospital bills and, indeed, funeral bills.
REFERENCES
1. University of Michigan (July 12, 2004). U-M physicist: Smart cruise control eliminates traffic jams. Press release.
2. L. C. Davis (2004). "Effect of adaptive cruise control systems on traffic flow". Physical Review Letters E 69 (6): 066110 (article ID; no page reference).
3. CY Liang, H Peng (1999). "Optimal Adaptive Cruise Control with Guaranteed String Stability". Vehicle System Dynamics 32 (4-5): 313-330.
4. P Venhovens, K Naab, B Adiprasito (2000). "Stop and Go Cruise Control". Proc. FISITA World Automotive Congress, Seoul, Korea.
5. L. C. Davis, Effect of adaptive cruise control systems on traffic flow Physics Department, University of Michigan, Ann Arbor, Michigan 48109, USA The American Physical Society (Received 27 October 2003; revised 22 January 2004; published 4 June 2004)
WEBSITES
1. siliconchip.com.au/cms/A_105086/article.html
2. audiaudi/com/en1/glossary/adaptive_cruise_control.html
3. pcmagencyclopedia
4. forden/innovation/safety/accidentAvoidance/adaptiveCruiseControl.html
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.doc   ACC adaptive cruise control full report.doc (Size: 76.5 KB / Downloads: 742)

ADAPTIVE CRUISE CONTROL
INTRODUCTION
Mentally, 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.
WHY ADAPTIVE CRUISE CONTROL?
Comfortable 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 driverâ„¢s 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.
ADAPTIVE CRUISE CONTROL
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 that 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 adjusting the vehicle speed and distance to that of a target vehicle. ACC uses a long range radar sensor to detect a target vehicle up to 200 meters in front and automatically adjusts the ACC vehicle speed and gap accordingly. ACC automatically decelerates or accelerates the vehicle according to the desired speed and distance settings established by the driver. As per standard cruise control the driver can override the system at any time.
Figure: THE CONCEPT OF ACC.
HOW DOES IT WORK?
The radar headway sensor sends information to a digital signal processor, which in turn translates the speed and distance information for a longitudinal controller. The result? 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 adaptive cruise control (ACC) system depends on two infrared sensors to detect cars up ahead. Each sensor has an emitter, which sends out a beam of infrared light energy, and a receiver, which captures light reflected back from the vehicle ahead.
The first sensor, called the sweep long-range sensor, uses a narrow infrared beam to detect objects six to 50 yards away. At its widest point, the beam covers no more than the width of one highway lane, so this sensor detects only vehicles directly ahead and doesn't detect cars in other lanes. Even so, it has to deal with some tricky situations, like keeping track of the right target when the car goes around a curve. To deal with that problem, the system has a solid-state gyro that instantaneously transmits curve-radius information to the sweep sensor, which steers its beam accordingly.
Another challenge arises when a car suddenly cuts in front of an ACC-equipped car. Because the sweep sensor's beam is so narrow, it doesn't "see" the other car until it's smack in the middle of the lane. That's where the other sensor, called the cut-in sensor, comes in. It has two wide beams that "look" into adjacent lanes, up to a distance of 30 yards ahead. And because it ignores anything that isn't moving at least 30 percent as fast as the car in which it is mounted, highway signs and parked cars on the side of the road don't confuse it.
Information from the sensors goes to the Vehicle Application Controller (VAC), the system's computing and communication center. The VAC reads the settings the driver has selected and figures out such things as how fast the car should go to maintain the proper distance from cars ahead and when the car should release the throttle or downshift to slow down. Then it communicates that information to devices that control the engine and the transmission.
There are several inputs:
System on/off: If on, denotes that the cruise-control system should maintain the car speed.
Engine on/off: If on, denotes that the car engine is turned on; the cruise-control system is only active if the engine is on.
Pulses from wheel: A pulse is sent for every revolution of the wheel.
Accelerator: Indication of how far the accelerator has been pressed.
Brake: On when the brake is pressed; the cruise-control system temporarily reverts to manual control if the brake is pressed.
Increase/Decrease Speed: Increase or decrease the maintained speed; only applicable if the cruise-control system is on.
Resume: Resume the last maintained speed; only applicable if the cruise-control system is on.
Clock: Timing pulse every millisecond.
There is one output from the system:
Throttle: Digital value for the engineer throttle setting.
ADAPTIVE CRUISE CONTROL FEATURES
o Maintains a safe, comfortable distance between vehicles without driver interventions
o Maintains a consistent performance in poor visibility conditions.
o Maintains a continuous performance during road turns and elevation changes
o Alerts drivers by way of automatic braking.
ADVANTAGES
Some of those advantages include:
¢ Its usefulness for long drives across 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. Such drivers should note, however, that a cruise control may go over its setting on a downhill which is steep enough to accelerate with an idling engine.
¢ Reduction in accident rate for vehicles fitted with collision avoidance type systems
¢ Reduction in driver fatigue
¢ Interconnection to more advanced future systems.
LIMITATIONS
One of the biggest challenges in designing ACC systems today are the costs associated with the robust system. Though current costs are substantial, they are slowly decreasing.
Auto manufacturers stress that advanced cruise control does not drive the car for you, and it's not meant to be used in heavy traffic. But, for long trips, it's a convenience that allows you to focus more on your driving.
CONCLUSIONS
Despite the introduction of the system to the market place, these are still early days. The current system can measure up to 150m ahead of the car and reduce the car's speed if an obstruction appears. What it can't do, at the moment, is bring the car to a halt.
Whatever happens, the ACC market looks set to explode. The project and implimentationed figures make startling reading. In 2002 there are no more than 100,000 vehicles fitted with ACC, but that figure is set to reach eight million in four years' time, with Europe, South-East Asia and the US accounting for about a third each. Around 17% of all European-built cars are likely to have ACC fitted as standard by then.
Expansion is bound to slow down thereafter, but by 2010 the global market will be 11.5 million units, representing an industry value of around $2.4 billion - and enormously more than that saved in repair bills, hospital bills and, indeed, funeral bills.
REFERENCES
1. University of Michigan (July 12, 2004). U-M physicist: Smart cruise control eliminates traffic jams. Press release.
2. L. C. Davis (2004). "Effect of adaptive cruise control systems on traffic flow". Physical Review Letters E 69 (6): 066110 (article ID; no page reference).
3. CY Liang, H Peng (1999). "Optimal Adaptive Cruise Control with Guaranteed String Stability". Vehicle System Dynamics 32 (4-5): 313-330.
4. P Venhovens, K Naab, B Adiprasito (2000). "Stop and Go Cruise Control". Proc. FISITA World Automotive Congress, Seoul, Korea.
5. L. C. Davis, Effect of adaptive cruise control systems on traffic flow Physics Department, University of Michigan, Ann Arbor, Michigan 48109, USA The American Physical Society (Received 27 October 2003; revised 22 January 2004; published 4 June 2004)
WEBSITES
1. siliconchip.com.au/cms/A_105086/article.html
2. audiaudi/com/en1/glossary/adaptive_cruise_control.html
3. pcmagencyclopedia
4. forden/innovation/safety/accidentAvoidance/adaptiveCruiseControl.html
5. SEMINAR TOPIC FROM :: edufiveseminar and presentationtopics.html
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09-05-2010, 01:36 AM


.docx   ACC_Presentation.docx (Size: 3.37 MB / Downloads: 180)

Adaptive Cruise Control


An ACC system is designed to assist the driver when following a vehicle traveling in the same lane and direction.

Conventional Cruise Control Operation

A typical conventional cruise control system controls the vehicle speed by adjusting throttle position to maintain a speed set by the driver. A control unit compares the actual vehicle speed and the desired set speed. If there is a difference between these two values, a signal is sent to a throttle position actuator to adjust the throttle position to bring the vehicle to the set speed. Depending on vehicle make and model, throttle position is achieved using vacuum-powered or electronically controlled actuators.

Adaptive Cruise Control ACC Overview

ACC 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.

Adaptive Cruise Control

ACC systems allow for a set following distance or time interval between the ACC vehicle and the forward vehicle, as well as a set speed. Driver convenience is enhanced since fewer accelerating and braking operations are necessary. The set distance (timed in seconds) is the desired distance between the ACC vehicle and the forward vehicle. When a forward vehicle is detected, controlling acceleration and braking operations without driver intervention maintains the set distance between vehicles. 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.
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01-10-2010, 03:49 PM


.docx   Adaptive Cruise Control (ACC).docx (Size: 2.99 MB / Downloads: 204)
ADAPTIVE CRUISE CONTROL

INTRODUCTION
Every day 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. The concept of assisting driver in longitudinal vehicle control to avoid collisions has been a major focal point of research at many automobile companies and research organizations. The idea of driver assistance was started with the ‘cruise control devices’ first appeared in 1970’s in USA. When switched on controls the vehicle speed by adjusting throttle position of engine to maintain a speed set by the driver. A control unit compares the actual vehicle speed and desired set speed. If there is a difference between these two values, a signal is sent to the throttle position actuator to adjust the throttle position to bring the vehicle’s speed to the set speed. But it could not consider the other vehicles on the road.
An ‘Adaptive Cruise Control’ (ACC) system developed as the next generation assisted the driver to keep a safe distance from the vehicle in front. ACC is an automotive feature that allows a vehicle's cruise control system to adapt the vehicle's speed to the traffic environment. A radar system attached to the front of the vehicle is used to detect whether slower moving vehicles are in the ACC vehicle's path. If a slower moving vehicle is detected, the ACC system will slow down the vehicle and control the clearance, or time gap, between the ACC vehicle and the forward vehicle. If the system detects that the forward vehicle is no longer in the ACC vehicle's path, the ACC system will accelerate the vehicle back to its set cruise control speed. This operation allows the ACC vehicle to autonomously slow down and speed up with traffic without intervention from the driver. The method by which the ACC vehicle's speed is controlled is via engine throttle control and limited brake operation. This system is now available only in some luxury cars like Mercedes S- class, Jaguar, Volva trucks etc. The U.S. Department of transportation and Japan’s ACAHSR have started developing ‘Intelligent Vehicles’ that can communicate with each other with the help of a system called ‘Cooperative Adaptive Cruise control”.

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23-12-2010, 02:11 PM

Prepared by:Gurulingesh R.



.ppt   aftab-1.ppt (Size: 628 KB / Downloads: 222)

Roadmap
Introduction to RTS
Problem Definition / Motivation
Adaptive Cruise Control (ACC)
Driver Models
Functional Model & Task Model
Extensions to Functional Model
Conclusion & Future Work
References
Functional Design & Mapping
What is “real” about real-time?
computer world

e.g., PC
average response for user
Interactive
occasionally longer
reaction: user annoyed
computer controls speed of user

“computer time”
real world

Industrial system, airplane
environment has own speed
reaction too slow: deadline miss
reaction: damage, pot. loss of human life
computer must follow speed of environment
“real-time”

Real-Time Systems
A real-time system is a system that reacts to events in the environment by performing predefined actions


Real-Time Systems: Properties of Interest

Safety: Nothing bad will happen.
Liveness: Something good will happen.
Timeliness: Things will happen on time - by their deadlines, periodically, ...
In a Real-Time System…
correct value delivered too late is incorrect
e.g., traffic light: light must be green when crossing, not enough before
Real-time:
(Timely) reactions to events as they occur, at their pace: (real-time) system (internal) time same time scale as environment (external) time

Types of RT Systems
Dimensions along which real-time activities can be categorized:
how tight are the deadlines?
--deadlines are tight when
laxity (deadline -- computation time) is small.
how strict are the deadlines?
what is the value of executing an activity after its deadline?
what are the characteristics of environment? how static or dynamic must the system be?
Hard, soft, firm
Timing Constraints
Real-time means to be in time --- how do we know something is “in time”? how do we express that?
Timing constraints are used to specify temporal correctness e.g., “finish assignment by 2pm”, “be at station before train departs”.
A system is said to be (temporally) feasible, if it meets all specified timing constraints.
Timing constraints do not come out of thin air: design process identifies events, derives models, and finally specifies timing constraints
Overall Picture

Timing Properties
Periodic
activity occurs repeatedly
e.g., to monitor environment values, temperature, etc.
Aperiodic
can occur any time
no arrival pattern given
Sporadic
can occur any time, but
minimum time between arrivals


Who initiates (triggers) actions?

Example: Chemical process
controlled so that temperature stays below danger level
warning is triggered before danger point
…… so that cooling can still occur
Two possibilities:
action whenever temp raises above warn -- event triggered
look every int time intervals; action when temp if measures above warn -- time triggered
Other Issues to worry about
Meet requirements -- some activities may run only:
after others have completed - precedence constraints
while others are not running - mutual exclusion
within certain times - temporal constraints
Scheduling
planning of activities, such that required timing is kept
Allocation
where should a task execute?
Project Motivation
Motivation (Cont…)
Partitioning of system into TT and ET domains
Process Mapping
Optimization of parameters corresponding to communication protocol.
Sequence and Slots of TDMA (TTC)
Priorities of Messages (ETC)
Schedulability
Adaptive Cruise Control
Adaptive Cruise Control:

automatically adjusts vehicle speed to maintain a driver-selected safe distance from the vehicle ahead in the same lane.
It then returns to the set speed when traffic clears.

Requirements:

The speed should be kept close to the SET speed, if there is no vehicle ahead.
Timegap should be maintained at x sec.
Manual intervention, UI, etc…
Functions Identified
Computing Current speed of our vehicle
Leading Vehicle related Task
Controlling Speed of our Vehicle
Controlling the Throttle
Controlling the Brake
Detecting Manual Intervention
UI to the Driver
Periodicity of Tasks
Hard, Firm; Periodic, Aperiodic…
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09-04-2011, 03:49 PM

hi ,
seminar and presentation report and ppt on adaptive cruise control available in several pages see some of them
topicideashow-to-adaptive-cruise-control-full-report
topicideashow-to-adaptive-cruise-control-full-report?page=2
topicideashow-to-seminar and presentation-report-on-cruise-control-devices
topicideashow-to-cruise-control-devices--5439
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27-01-2012, 02:35 PM

adaptive cruise control PPT


.pptx   BHATIA.PPT.pptx (Size: 2.34 MB / Downloads: 93)

WHY ADAPTIVE CRUISE CONTOL

TO MAINTAIN COMFORTABLE DISTANCE

FOR DRIVING SAFETY

BETTER TRAFFIC FLOW

SPEED MAINTAINENCE

CONSISTENT IN POOR VISIBILITY CONDITIONS AND ELEVATION CHANGES


ADVANTAGES


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.

Its usefulness for long drives across sparsely populated roads. This usually results in better fuel efficiency


LIMITATIONS


One of the biggest challenges in designing ACC systems today are the costs associated with the robust system. Though current costs are substantial, they are slowly decreasing.

Auto manufacturers stress that advanced cruise control does not drive the car for you, and it's not meant to be used in heavy traffic. But, for long trips, it's a convenience that allows you to focus more on your driving.



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15-02-2012, 03:21 PM

to get information about the topic cruise control seminar and presentation full report ,ppt and related topic refer the link bellow

topicideashow-to-cruise-control-devices--23578

topicideashow-to-adaptive-cruise-control-full-report?pid=64145#pid64145

topicideashow-to-cruise-control-devices--5439

topicideashow-to-cruise-control-system
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