An Improved Algorithm for Collision Avoidance System among Vehicles Selvendran .S Dr. S. Vasantharathna Electrical and Electronics Department Coimbatore Institute of Technology Coimbatore, India sselvendran6@gmail.com Electrical and Electronics Department Coimbatore Institute of Technology Coimbatore, India vasantharathna@cit.edu.in Abstract— This paper proposes an Intelligent approach for Collision Warning and Avoidance between vehicles in straight roads and also at intersection roads using Vehicle to Vehicle (V2V) communication and Vehicle to Infrastructure (V2I) communication. It comprises of a wireless automotive communication protocol where automobiles send messages to each other with information about what they are doing. This data would include speed, geographical location, direction of travel, braking and loss of stability. In the intersection roads or in the highways when the vehicles come to collide with each other due to the improper functioning of drivers, by using V2V and V2I communication, vehicles automatically gets the control from the driver and acts to the emergency situation by applying the brakes or changing the lane etc. This system considers safety and better traffic management by using a Dedicated Short Range Communication (DSRC) called ZigBee (802.15.4) as a wireless protocol, Ultrasonic sensor, Compass sensor, Object sensor, and RF Transceiver which are controlled by using ATmega162V microcontroller. In this paper a prototype for Collision avoidance system is shown by using a Robotic Cars with the sensors implemented on it. Keywords— V2V, V2I, ZigBee, Ultrasonic Sensor, Compass Sensor, Object Sensor, Robotic Car. I. INTRODUCTION ccidents are the major cause for the loss of human lives, which have a big number for human deaths from vehicular accidents than deadly diseases or natural disasters. About 70% of roadway collisions could be avoided if the driver was provided with the warning of about one-half second before the collision. According to the latest road transport ministry report an Indian dies in a road accident for every 3 minutes, since India is experiencing a car boom. India is ranked second in the world for estimated road traffic deaths per year, according to WHO’s global status report on road safety published in 2013 [9]. From India’s premier automotive magazine, there are currently around 1.6 to 1.7 million new cars bought each year and these figures are expected to double by the year 2015. But there are already large congestion problems on Indian streets. The number of accidents continues to rise, even though there is a technological innovations and developments in the vehicle safety. This is especially true for the accidents at the intersection roads. Accident rate is more at the intersection roads than at the straight roads. Most of these accidents take place at rural areas. Thus an intersection A collision warning system must be implemented as a part of vehicle safety systems, inorder to reduce the large number of road accidents. To be most effective, such a system should have the capability of supporting real time systems that can warn potential drivers of an impending collision. A study conducted by the National Highway Traffic Safety Administration (NHTSA) on intersection-related crashes in 2010 concluded that 44.1 percent of intersection-related crashes were most directly attributed to inadequate driver surveillance, compared to only 7.3 percent in non-intersectionrelated crashes. In this paper, a safety system is proposed for the straight roads and intersection roads, thus reducing the number of fatal accidents at the roads by giving a proper warning to the driver by displaying that there is an approaching vehicle with a particular speed at particular distance. And if the driver doesn’t notice and respond to the warning message then the system automatically takes the control from the driver and acts to emergency situation by applying brakes or changing lane etc. A Vehicle to Vehicle communication and Vehicle to Infrastructure communication technology is used for driver assistance system and collision warning system. The communication is mainly achieved by an automotive wireless protocol which provides a 360 degree view of the vehicle surroundings. The different participants for the automotive wireless protocol are DSRC, ZigBee, WiFi, Bluetooth, UWB [14]. From this, the best suitable protocol for this kind of application is ZigBee (IEEE 802.15.4) which has a coverage range of 10-100 meters with the less power consumption [11]. For collision avoidance, there were several options to choose from in terms of selection of sensor. These includes infrared, LIDAR [6], camera [5] and ultrasonic sensors [4]. Infrared sensors, despite being cheap, were not a suitable choice as in daytime outdoor operations, infrared radiation from the Sun would have also interfered with sensors. LIDAR is an accurate, reliable and effective collision avoidance and obstacle detection system, however, it is an expensive, unfeasible option compared to other solutions and thus was not chosen. Camera for the front side was selected for performing image processing because it is an accurate, sophisticated method of determining obstacle position and ensures that the vehicle moves in the correct direction to avoid collision. Ultrasonic sensors have been widely used to detect and avoid obstacles in mobile robot and automobile applications [4]. Ultrasonic sensors were chosen and installed on the front side of the vehicle because of their accuracy, speed, reliability and effectiveness in detecting distance from obstacles in addition to the fact that more cameras for these sides would have resulted in slow, in effective and resourceintensive image processing. Object sensors are used at the rear and right sides of the vehicle to detect the back approaching vehicles and to see the overtaking vehicles. Compass sensor is used to determine the heading and direction of travel of the vehicle. Compass sensor is used instead of Global Positioning System (GPS) [7]. GPS does not provide correct coordinates value when the vehicle is moving in a tunnel due to the blockage of satellite signal and also there is no change in values for small movements. The operation of all the sensors is controlled by the ATmega162 Microcontroller. ZigBee is used which broadcasts the values obtained from the onboard sensors. Here an intelligent traffic management system is established [16]. By using compass sensor in each vehicle, this intelligent system calculates the number of vehicles present in each direction and it is programmed such that, based on the density of the vehicles the traffic light time interval varies for each direction. In [3], Suhas Chakravarty and Varun Jain proposed a low cost driver assistance using a ZigBee protocol, describing the usage of different ZigBee nodes placed at the sides of the roads [2]. But this type of implementation is difficult in achieving and cost effective. In [6], an optical vehicle-to-vehicle (V2V) communication system based on an optical wireless communication technology using an LED transmitter and a camera receiver is proposed, which employs a special CMOS image sensor, i.e., an optical communication image sensor (OCI). This technology is helpful in identifying the obstacles in straight to this vehicle but not efficient in intersection roads. In this work, a simple prototype containing two Robotic cars which performs communication between them and avoids collision is demonstrated. This paper is organized as follows. Section II describes the Vehicle to Vehicle safety application, Section III explains the block diagram, Section IV explains the hardware components used in this project, Section V describes the mathematical modeling, Section VI explains the concepts of Collision warning and Avoidance system, Section VII explains Software Development, Section VIII shows the Result and Discussion and Section IX concludes this paper. II. 7. If the vehicle suddenly breaks in the middle of the road. When the vehicle detects some risks, it issues the warning message. Based on the Vehicle to Vehicle communication and Vehicle to Infrastructure communication, the system provides the following safety warnings. 1. Forward Collision Warning (FCW). 2. Rear Collision Warning (RCW). 3. Intersection Collision Avoidance (ICA). 4. Blind Spot and Lane Change Warning. 5. Do not pass warning. 6. Zone Warning. Each Vehicle continuously broadcasts its speed, position, and its driving direction. III. BLOCK DIAGRAM The block diagram for the manual controlled vehicle is shown in Fig.1 and for Autonomous vehicle is shown in Fig.2. Various sensors are interfaced to microcontroller which controls the motion of the car. Fig. 1. Manual controlled Vehicle VEHICLE-TO-VEHICLE SAFETY APPLICATION From the Statistics of road accidents, the major reasons for the road accidents are explained below [10]. 1. If the front vehicle suddenly stops or slows down. 2. If the vehicle is in loss of control. 3. If the vehicle changes lanes suddenly. 4. If the vehicle drives across the roads junction where is absent of traffic signal lights. 5. If the vehicle does not follow the traffic rules. 6. If the road is in congestion or abnormal. Fig. 2. Autonomous Vehicle IV. HARDWARE The following are the main components used to design the prototype. A. Robotic Car The Robotic car consists of a chassis of 27 cm long and 1cm ground clearance with steer mechanism for lateral control and drive mechanism for longitudinal control, communication modules for vehicle communication and control unit for controlling the autonomous nature of the vehicle. A high Torque Futaba S3010 Servomotor is used for steering, which is controlled by the PWM signal and two DC motors with appropriate gear reduction arrangement are used for longitudinal drive mechanism. DC motor is driven by HBridge motor driver. The Robotic car is driven by 7.2V/2000mAh, Nickel Cadmium re-chargeable battery pack [8]. sensor has a magnetic strip which aligns itself with magnetic north, and from this, orientation can be determined. Thus, because a compass sensor is used to determine just the direction of a magnetic field, they are considered scalar magnetometers. It has a features of I2C interface, 1-2 degree heading accuracy, Integrated 12 bit ADC and 160 Hz max data rate. E. Object Sensor Object sensor is a sensor able to detect the presence of nearby objects without any physical contact. It often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different object sensor targets demand different sensors. For example, a capacitive or photoelectric sensor might be suitable for a plastic target and an inductive object sensor always requires a metal target. F. ZigBee Module Fig.3. Robotic Car B. ATmega162 Microcontroller ATmega162 is a High-performance, Low power AVR 8-bit Microcontroller based on the advanced RISC Architecture. It is a 40 pin PDIP with 35 programmable I/O lines operates between 2.7 - 5.5V. It achieves a throughput of 16 MIPS at 16 MHz and has a high endurance Non-volatile memory segments with 16KB of programmable Flash memory, 512Bytes EEPROM, 1KB internal SRAM and a JTAG interface for on-chip debugging. Its peripheral features include two 8-bit Timer/counters and two 16-bit Timer/counters, real time counter with separate oscillator, six PWM channels, Dual programmable serial USARTs and a programmable watchdog timer. C. Ultrasonic Sensor HC-SR04 ultrasonic ranging modules are used to calculate distance of obstacles from the vehicle. These sensors have a maximum range of 500 cm and maximum effectual angle of 15โฐ. It is also known as transceivers when they both send and receive, but more generally called transducers, work on a principle similar to radar or sonar, which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. Active ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor, measuring the time interval between sending the signal and receiving the echo to determine the distance to an object. Sensor is connected to AVR and power supply via a 4 pin wire connector. D. Compass Sensor A compass sensor is a navigational instrument which is sensitive to the magnetic field of the earth. A typical compass IEEE 802.15.4/ZigBee is a standard protocol for Low-Rate Wireless Personal Area Networks (LR-WPAN). Its main features are network flexibility, low data rate, low cost and very low power consumption, which make it suitable for an adhoc network between inexpensive fixed, portable and moving devices. The IEEE 802.15.4 protocol includes a PHY layer and MAC sub-layer for the LR-WPAN. The PHY layer offers three operational frequency bands; there are 27 channels allocated in the 802.15.4 range, with 16 channels in the 2.4 GHz band, 10 channels in the 915 MHz band, and 1 channel in 868 MHz band [11], [13]. Parameters ZigBee Value Transmission Range(Meters) 1 - 100 Battery life (days) 100 – 1000 Network size(# of nodes) > 64,000 Throughput (kb/s) 20 - 250 Fig.4. ZigBee Specification G. RF Module A RF module (radio frequency module) is a small electronic device used to transmit and/or receive radio signals between two devices. In an embedded system it is often desirable to communicate with another device wirelessly. This wireless communication may be accomplished through optical communication or through Radio Frequency (RF) communication. For many applications the medium of choice is RF since it does not require line of sight. RF communications incorporate a transmitter and/or receiver. It can send only 0 and 1 value. H. Liquid- Crystal Display It is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals. A 20x4 LCDs are used to display the information which is interfaced to AVR microcontroller. V. MATHEMATICAL MODELLING From Equation (1), ๐ = ๐๐, rewriting the equation, The steering of the vehicle is controlled by the high precision servo motor. By basic physics, the relation between the linear and angular velocity is given as, ๐ฃ = ๐๐ (1) where ‘v’ is the linear velocity of the vehicle, ‘r’ is the radius and ‘ω’ is the angular velocity. From the values of the current velocity and the angular position of the vehicle, the position of the vehicle at any point can be accurately given by the fundamental relationship between the parameters. The relation between the linear and the angular velocity is shown in Fig.9. The horizontal and vertical components of the velocity can be decomposed as shown in Fig.10. Fig. 5. Angular velocity and Linear velocity Fig. 6. Velocity components The horizontal and vertical component of velocity is related to their corresponding displacements as given in equations (2) and (3). ๐๐ฅ ๐ฃ๐ฅ = (2) ๐๐ก ๐ฃ๐ฆ = ๐๐ฆ ๐๐ก (3) ๐ก ๐ก ๐ฅ = ∫0 ๐ฃ(๐ก) cos ๐(๐ก) ๐๐ก (4) (5) Similarly for y co-ordinate, ๐ก ๐ฆ = ∫0 ๐ฃ(๐ก) sin θ(๐ก) ๐๐ก (6) In differential form, it can be given in equations (7) and (8). ๐ฅฬ = cos ๐ (๐ก). ๐ฃ(๐ก) (7) ๐ฆฬ = sin ๐ (๐ก). ๐ฃ(๐ก) (8) (9) The vehicle model can be thus given as, ๐ฅฬ cos ๐ cos ๐ 0 [๐ฆฬ ] = [ sin ๐ ] [๐ฃ] = [ sin ๐ ] ๐ฃ + [0] ๐ 1⁄๐ 0 1 ๐ฬ (10) where ๐ฅฬ denotes the linear velocity in x direction which depends on cosine function, ๐ฆฬ represents linear velocity in y direction which corresponds to sin function and ๐ฬ corresponds to angular velocity. VI. COLLISION WARNING AND AVOIDANCE SYSTEM A. Description of Concepts This section describes the detailed working of this project, explains about the working of Vehicle to Vehicle communication and Vehicle to Infrastructure communication between Vehicles. Here a Collision Avoidance System is implemented for two cases, one for Straight roads and another for Intersection roads. Two Robotic cars are used for prototyping, each vehicle is equipped with the ATmega162V microcontroller, and interfaced with the different sensors for obstacle detectance, and direction of travel etc. ZigBee is used as an automotive wireless protocol used to broadcast the information continuously from each vehicle. The information includes the speed of the vehicle, heading and distance between the nearby vehicle. At Intersection there are different points which are conflict to collision [1]. Consider the collision avoidance in straight roads, ultrasonic sensor is placed infront of the vehicle, which is controlled by the microcontroller, continuously emits the ultrasonic waves, the waves after striking any obstacle bounces back and reach the receiver. By measuring the time it take for the whole process to complete and by using simple arithematic, can measure distance to the obstacle. To calculate distance (cm) = Where ‘x’ and ‘y’ are the displacement in horizontal and vertical direction respectively. The position of the vehicle is given in equations (4), (5) and (6). ๐ฅ = ∫0 ๐ฃ๐ฅ (๐ก)๐๐ก 1 1 ๐ = ๐ฃ and ๐ฬ = ๐(๐ก) = ๐ฃ(๐ก) ๐ ๐ ๐๐ข๐๐ ๐ ๐ค๐๐๐กโ 58 The vehicle 1 continuously scans the presence of any vehicle within the coverage area of the current vehicle. If it detects the presence of any vehicle then by receiving the information broadcast by that vehicle, and obtained the direction of travel. If that value is same to that of the vehicle 1, then that both vehicles are in the same road ie, Straight road, and if that values are different, then the vehicles are at intersection roads. Warnings are provided to the driver inorder to avoid the collision and if the driver doesn’t respond to the situation then the vehicle automatically takes the control from the driver and acts to the emergency situation by applying brakes. B. In Straight Roads The Flow chart for the collision avoidance system at straight roads is shown in Fig. 7. In that each vehicle is implemented with the ultrasonic sensor at the front. Vehicles broadcast their speed and direction of travel through ZigBee. By using compass sensor values the system checks whether the vehicle near to it is in the same heading or at intersection. Ultrasonic sensor continuously checks the presence of any obstacle or any vehicle moving infront. The system warns the driver regarding collision ahead if the distance measured by the ultrasonic sensor decreases and if the driver neglects to reduce the speed then the system immediately reduces the speed and applies the brake automatically when the distance decreases below the threshold value. Through this system the V2V features like Forward Collision Warning, Rear Collision Warning, Blind spot and Lane change Warning is achieved. DUDE or USBasp. Fig. 8 shows the steps for software development. Fig. 8. Steps for software development The snapshot of C coding for the proposed system using AVR Studio6 is shown in Fig. 9. Fig. 9. Coding in AVR Studio6 VIII. RESULTS AND DISCUSSION Fig. 7. Flowchart VII. SOFTWARE DEVELOPMENT ATmega162V microcontroller is used to control the proposed system. Software development gives the pep and functionality to the system. The coding for this system is written in embedded C language and AVR studio6 is used as compiler. AVR functions like UART, timer, ADC, interrupts, etc are handled by AVR studio6 and provide the facility to write the program in embedded ‘C’. The resultant of the program is obtained in hex code file which burn into flash memory of AVR microcontroller using a AVR programmer called AVR The results for this proposed system is shown through the Hardware Implementation. Two Robotic cars are made to run in the small track. The first vehicle (Robotic car 1) is autonomous and the second vehicle (Robotic car 2) is of manual type. Consider the two cars going in a straight road one after the another and if the first car slows down the speed then the ultrasonic sensor placed in the second car will continuously measure the distance from the forward car. If that distance reduces below 80 cm then the system will warn the driver regarding collision ahead. If the first car suddenly stops, then the second car provides warning to the driver and at the same time reduces the speed by decreasing the PWM values given to the motor. If the distance decreases below the threshold value of 10 cm, then the system completely stops the second car which is conflict to collision. The result is shown in the Fig. 10. Fig. 10. Prototype Distance (cm) 33 50 72 103 Ton (ms) Toff (ms) Duty Cycle (%) 0.6 2.4 1.2 1.8 1.5 1.5 1.8 1.2 Fig. 11. Obtained Value Distance = 33cm 20 40 50 60 Distance = 50cm Distance = 72cm Distance = 103cm Fig. 12. Waveforms The duty cycle for different values of distance measured by ultrasonic sensor was tabulated and is shown in Fig. 11. The Fig. 12 shows the waveforms of PWM obtained from CRO for different distance values. These PWM values are given to the DC motors for controlling the speed when the obstacle approaches infront of the vehicle. IX. CONCLUSION A Low-cost and an Improved approach for Collision Warning and Avoidance system is proposed. Through this project, a miniature Robotic car was developed which is capable of performing the basic tasks a normal vehicle has to do. In this project, we have detected the obstacles with the help of Ultrasonic sensors, then the collision warning is given to the driver and also automatic collision avoidance is achieved successfully using Vehicle to Vehicle communication. Although this project is done using a simple prototype, it can be implemented on actual cars also, as the basic concepts remain the same. If the ultrasonic sensors or Object sensors are placed in the sides and rear of the vehicle, then the driver can get the 360 degree view of their vehicle. This system will be helpful in minimizing the accidents. 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