An Analysis Of Driverless Cars

Abstract- Driverless cars are the promising approach to reduce the traffic problems. In driverless cars the frequently changing state of the road due to obstacles is controlled by array of sensors, which acknowledges the presence of obstacles on the driving path and creates the suitable path by frequently updating the route. This paper describes the efficient Doppler radar system and specialized algorithms to measure the speed of a vehicle used in autonomous vehicles. The velocity, acceleration and the position of a moving target can be determined by observing the Doppler signal at several points in space. This paper also gives a brief idea of other sensors integrated with radars in autonomous vehicle.

Introduction An autonomous vehicle
The sensors like LIDAR, Cameras, RADAR, GPS, and Ultra sonic sensors play a very significant role. LIDAR which is abbreviated as Light Detecting And Ranging in most of the cases are mounted at the top of the vehicle in order to scan and capture 360° image of its immediate surrounding for the creation of the dynamic three dimensional map of the environment. LIDAR uses rapid laser pulses and detects edges of the road and help to identify the lane marks. The cameras basically used to detect traffic lights, road signs, and to look after the pedestrians and other obstacles. RADAR (Radio Detection And Ranging) is used to determine the speed, direction, range, altitude of the object and allow the system to adjust the speed of the car. Radar uses electromagnetic waves. Here in driverless cars we use Doppler radar to determine the velocity and direction. Ultrasonic sensors are mounted on the wheels. These can detects the curbs and other vehicles by producing the ultrasonic waves while parking. Ultrasonic sensors can work in any lightning conditions and these play a vital role in parking assistance system. GPS abbreviated as Global Positioning System provides information of the locations in all whether conditions. GPS continuously updates with real time changes. Based on the information obtained from the GPS the vehicle
The radiated electromagnetic energy travels at a constant speed at approximately the speed of light. It can travel at the speed of 300,000 km/h. The Doppler radar transmits the electromagnetic waves, if these waves meet any surface it get reflected back and is received at the same place of the origin. These reflected waves are used in determining the speed and direction of the opponent vehicle in autonomous cars. The constant speed of the electromagnetic wave allows the determination of the distance between the reflecting objects. The
Doppler radar works on the principle of Doppler Effect. Doppler Effect is the frequency shift between the transmitted and the received signal observed when source is transmitting an electromagnetic wave moving relative to an observer. The difference in the frequency between transmitter and the receiver is known as Doppler shift or the Doppler frequency. The transmitted and received signals can be represented as
ET = A sin 2πft (12.25)
ER = B sin [2πft – φ] (12.21)
Where A and B are constants and φ is the phase shift due to propagation delay time.
The phase shift can be given