Published on March 9, 2014
PRESENTED BY GOKUL.G EPAKEEC027 GUIDED BY Asst.Prof.SAPNA ECE Dept.
INTRODUCTION Driver error is the most common cause of traffic accidents India contributes 6 % of the world's road accident deaths Cell phones in-car ,entertainment systems, more traffic and more complicated road systems making it more frequent Drowsiness of the driver and failure in taking sudden decisions adds up to the factors . The fully autonomous cars posses the technology which drives it the safest way possible and have been proved successful in this context till now .
What is a driverless car ? As the name says , this car does not need a driver to drive it . The passenger just has to feed in the destinations he want to reach and the car will take him to the destination . We can compare this with the “Autopilot” system we are familiar of . The difference here is that , the autopilot system just make the vehicle move in a predefined path or a straight path , but this system drives the vehicle through any roads of varying traffic density and topography , in the safest way .
About existing driverless cars.. A lot of experiments where done regarding this topic but the only successful , fully autonomous , driverless car was finally invented by a team of engineers in Google . Google Chauffer or Google Car is considered to be one of the best inventions in the last 25 years . Consisting of a whole lot of sensor systems and a powerful central processing unit , Google Car easily drives through any traffic conditions and topologies . It detects pedestrians , cyclists , traffic signals , oncoming vehicles , speed and distance to be maintained between successive vehicles etc .
Making the car driverless.. The systems used in the car are : LIDAR( Light Detection And Ranging) Automotive Radar System Ultrasonic Sensors Video Cameras GPS( Global Positioning System) Position Estimators Inertial Measurement Unit A central processing unit or computer unit to control all the above systems as well as systems like ABS (Antilock Braking System) , ESC ( Electronic Stability Control ) , Self Parking etc.
The LIDAR System The Light Detection And Ranging system can be considered as the eye of the car . It is a remote sensing technology which measures distance by illuminating a target with a light beam and analyses the reflected light . It uses Laser beams , ultra violet , visible light or near infrared light to image objects . It can target a wide range of materials . Here , a narrow laser beam is used , which maps physical structures with a high resolution . There are two types of LIDAR systems : Coherent and Incoherent . Here , a Coherent LIDAR system is used which uses Optical Heterodyne Detection , which yields more sensitivity than Incoherent systems , but at the expense of more complex transceiver components .
The LIDAR System….. The system uses Laser beams of wavelength 1550 nm which are “ eye-safe”. The scanning module used here is a Velodyne 64 beam laser module . The basic LIDAR system consists of a Laser range finder beam reflected using a rotating mirror . The laser beam is scanned around the scene to be digitized , in 3 Dimensions using an array of similar systems , gathering distance measures at specified angle intervals . The detector part uses two main technologies i.e, Solid State Photo detectors and Photomultipliers. The LIDAR sensors require info about their orientation and position , which they obtain from the GPS and the Inertial Measurement Unit .
The Automotive Radar System The Radar system used here is of 24GHz domain which have good performance in range and azimuth angle measurement . The range of radar systems used is up to 300m . The radar system are used for detecting oncoming vehicles , their speed , other obstacles , for self parking , blind spot detection , pre-crash detection etc. The Radar systems are installed on the bumper of the vehicle at the front as well as at the back side of the vehicle . For applications other than blind spot detection , higher precision , longer range and higher update rates are needed . Radar systems detect the surrounding environment and the central computer combines this result with that of the LIDAR system .
The Automotive Radar System….. The Radar system is mounted in the above way . The sensor IF-output signals are processed separately in the DSP control units and four target lists are sent to the central processor (radar decision unit) via CAN bus. Each single sensor measures the target range only. The data fusion is performed in the radar decision unit. The Application part means the unit to which the information gained is to be applied . The information include distance information of objects , relative velocities of objects and their angular positions .
How the car sees the world The information from the LIDAR system , the Radar Systems as well as The ULTRASONIC Sensors which are used for Blind Spot detection as well as to detect nearby objects and also some data from the video camera are combined by the central processing unit . By combining these data , a 3D map of the surroundings is generated by the central computer . The 3D map will include detailed info. about moving and stationary objects , like pedestrians , cyclists , other vehicles , edges of roads . Combining the 3D map with info. from the GPS module , the central processing unit controls the steering , accelerator brakes etc.
The Video Camera Video cameras are installed at the top of the front glass of the near the rear view mirrors. These cameras are used to detect the traffic lights , traffic signs , pedestrians etc. The traffic lights are detected by image processing which is done by the central processing computer. The computer processes the videos and detects whether traffic lights are red , yellow or green . If a red/yellow light is detected , the computer stops/slows down the vehicle . The Video Cameras also detect different road signs like “ STOP” signs , ZEBRA crossings , sign Boards etc .
The GPS and IMU Systems GPS ( Global Positioning System ) , uses satellites to gather information about the current position of the vehicle , the topology and by using the GPS a map of the area is loaded into the central computer . But data from GPS alone is less accurate . So , this data is combined with outputs from the IMU ( Inertial Measurement Unit ) . IMU is an electronic device which measures and gives information about the vehicle’s velocity , orientation , gravitational forces etc. IMU uses a combination of accelerometers , gyroscopes and magnetometers . An IMU helps GPS system to work when signals are unavailable such as in tunnels , buildings , bad weather conditions and when electromagnetic interference is present . By combining data from IMU-GPS systems , a map is developed and is compared with the 3D map prepared by the computer for better results . This system is also used in navigating the car by the user in which the passenger gives the destination he needs to reach using GPS systems .
The Central Computer All the data obtained from each and every sensor systems is fed to the central computer . The central computer is a very powerful processing unit mounted on the inside of the vehicle . Position Estimator Sensor is an important part of the vehicle , which is an ultrasonic sensor used to detect the current position of the vehicle and respond to even a small movement of the vehicle . It is used for constantly updating the position of the vehicle with respect to the 3D map . It is mounted near the left rear wheel . The central computer constantly receives data from the position estimator ( also called Wheel Encoder ) and combines it with the data from the other sensors . The computer uses this data to control the steering , accelerator , brakes etc . The computer also helps in navigating to a desired point through the shortest path . It is also used for limiting the speed of the vehicle .
Other Technologies Used In The Car Anti-lock brakes(ABS) Electronic stability control (ESC) Cruise control Lane Departure Warning System Self Parking Automated Guided Vehicle Systems Automotive Night Vision Adaptive Highbeam
Advantages Managing traffic flow to increase road capacity. Relieving vehicle occupants from driving allowing them to concentrate on other tasks or to rest during their journeys. To avoid accidents . Increasing roadway capacity by managing the distances between cars. The current location of vehicle can be determine using global positioning system (G.P.S) .
Disadvantages If the vehicle is using internet which is have less security then From the hackers point of view in some cases the vehicle can be switched off on the road(in rare cases) Hackers can change the rout which is plotted in the system(in rare cases) In case of failure of main sensor and backup sensors the vehicle can create a chance of accident Also , there is difficulty for the system to understand hand-signals .
Conclusion The driver less car is a technological masterpiece. It is boon for handicapped people and for those who feel uncomfortable while driving . It is very helpful in reducing the number of accidents . The high cost of the sensor systems is a factor which can adversely affect it . But mass production of the vehicle can reduce the effect . Also , if the nations like India approve such cars to be driven in the traffic , it will be very much helpful for us .
References http://en.wikipedia.org/wiki/driverless car http://autocontrols.com.au/ http://www.howstuffworks.com/cruise-control http://www.howstuffworks.com/electronic stability control
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