Collision Warning With Automatic Braking System For ...

International Journal of Mechanical Engineering Research. ISSN 2249-0019 Volume 5, Number 2 (2015), pp. 153-165 © Research India Publications http://www.ripublication.com

Collision Warning With Automatic Braking System For Electric Cars Kuchimanchi Chirantana and G V R N D Satya Sai Kanth GITAM UNIVERSITY, HYDERABAD CAMPUS, FLAT NO. 201, MY HOME JEWEL, MADINAGUDA, MIYAPUR, TELANGANA Telephone number: 040-67367013 Mobile number: +918500264077, +919866169898, Email: chirantanak@gmail. com satyasaikanth@gmail. com

ABSTRACT Automotive safety has gained an increasing amount of interest from the general public, governments and the car industry. This is more than justified by traffic accident statistics, as each year around 1. 2 million people die due to road traffic accidents. This paper presents a model of cost effective collision warning system for low budget cars. Rear-end collisions are common accident scenarios and a common cause of these accidents is driver distraction and thus not reacting in time. No vehicle system is a substitute for the most important safety feature in any vehicle the driver. Now a day’s many automobile manufacturers are harnessing innovative technologies to help alert drivers to avoid collisions and reduce the potential impact speed when a collision cannot be avoided. One of those systems is Collision Warning with Automatic Braking where the area in front of the vehicle is continuously monitored with the help of long range sensor and driver is warned in case of collision and along with brake support for collisions with other vehicles, both moving and stationary. Additionally, if the driver does not intervene in spite of the warning and the possible collision is judged to be unavoidable; brakes a r e a p p l i e d automatically to slow down the car. This aims at reducing impact speeds and thus the risk of consequences. Finally, it has been discussed how the benefit of such systems can be judged from reallife safety perspective using traffic accident statistics. Keywords: Collision, Ultrasonic Sensor, Arduino, Automatic Braking

INTRODUCTION: Collision warning system with automatic braking is a combination of several

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technologies. Over the years, automotive safety has gained an increasing amount of interest from the general public, governments, and the car industry. A successful way to attain continuous improvements in safety development is a working process based on real world situations and the feed-back of this information into the product development. This working method has been found very effective in passive safety development. The present study applies this working process into development of new active safety systems. Active safety systems require a wider scope of the study and performance goals, thereby expanding to accident occurrence beside injury protection and opponent vehicle beside host vehicle. The aim of this paper is to present some of the latest active safety development and to put them into context of the working process. Collision detection is done by using Ultrasonic sensor and Stop indication using flashing LED and LCD display. Braking is done using a servo motor connected to parking brake lever to ensure optimal braking force and minimum braking distance. Electro mechanical actuation using mechanical actuator making the operation extremely fast thereby safety ensured braking. Power of the prime mover is cutoff using a relay switch to reduce power wastage and break wear. All these devices are controlled using Arduino Mega 2560 which is a microcontroller programmed to do the specified task. LITERATURE SURVEY: Integrated safety systems can be broadly divided into two categories:  Collision avoidance: In this system the collision is avoided by the automatic braking, but the driver will not be warned in this type of system. There is a very good chance of wrongly interpreting the signals, especially in the case of radars or lasers. So this is not so effective method of automatic braking.  Collision mitigation system: In this system the sensors detect the possibility of collision but will not take immediate action. A warning will be sent to the driver in the form of a signal or a voice message. There is a threshold safe distance calculated by the system and if the driver fails to respond even when the vehicle crosses that region, then only brakes will be applied automatically. Even if there is a misinterpretation of signals, there is no problem because, the decision to apply brakes is left with the driver and the brakes are applied automatically only in the most emergency situations. Various advanced technologies assisting braking:  Emergency brake assist (EBA): It is a generic term for an automobile braking technology that increases braking pressure in an emergency situation. The first application was developed jointly by Daimler-Benz and TRW/LucasVarity. Research conducted in 1992 at the Mercedes-Benz driving simulator in Berlin revealed that more than 90% of drivers fail to brake with enough force in emergency situations. By interpreting the speed and force with which the brake pedal is pushed, the system detects if the driver is trying to execute an emergency stop, and if the brake pedal is not fully applied, the system overrides and fully applies the brakes until the Anti-lock Braking System (ABS) takes over to stop the wheels locking up.

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FIG 1: ELECTRONIC BRAKE ASSIST 

Electronic brake force distribution (EBD or EBFD): It is an automobile brake technology that automatically varies the amount of force applied to each of a vehicle's brakes, based on road conditions, speed, loading, etc. Always coupled with anti-lock braking systems, EBD can apply more or less braking pressure to each wheel in order to maximize stopping power whilst maintaining vehicular control. Typically, the front end carries the most weight and EBD distributes less braking pressure to the rear brakes so the rear brakes do not lock up and cause a skid. In some systems, EBD distributes more braking pressure at the rear brakes during initial brake application before the effects of weight transfer become apparent.

FIG 2: ELECTRONIC BRAKE FORCE DISTRIBUTION 

Autonomous emergency braking (AEB): It is an autonomous road vehicle safety system which employs sensors to monitor the proximity of vehicles in front and detects situations where the relative speed and distance between the host and target vehicles suggest that a collision is imminent. In such a situation, emergency braking can be automatically applied to avoid the

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Kuchimanchi Chirantana and G V R N D Satya Sai Kanth collision or at least to mitigate its effects. A recent study suggests that if all cars feature the system, it will reduce accidents by up to 27 percent and save up to 8000 lives per year. Anti-lock braking system (ABS): It is an automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding. It is an automated system that uses the principles of threshold braking and cadence braking which were practised by skillful drivers with previous generation braking systems. It does this at a much faster rate and with better control than a driver could manage. ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces; however, on loose gravel or snow-covered surfaces, ABS can significantly increase braking distance, although still improving vehicle control.

FIG 3: ANTI LOCK BRAKING SYSTEM Requirement: According to the road accident statics nearly 1. 3 million people die in road crashes globally. There is a need for more advanced safety technologies in automobiles. One among them is collision warning along with automatic braking in which the driver is warned in case of collision and brakes are applied by which there is a chance of reducing the number of accidents. The major causes of fatal accidents are the psychological factor such as sleep, inattention and medical disorders of the driver. So by this system the driver can be warned in case of any collision and necessary action can be taken by him in order to avoid accidents. Annual Global Road Crash Statistics  Nearly 1. 3 million people die in road crashes each year, on average 3, 287 deaths a day.  An additional 20-50 million are injured or disabled.  More than half of all road traffic deaths occur among young adults ages 15-44.  Road traffic crashes rank as the 9th leading cause of death and account for 2. 2% of all deaths globally.  Road crashes are the leading cause of death among young people ages 15-29, and the second leading cause of death worldwide among young people ages 514.

Collision Warning With Automatic Braking System For Electric Cars     

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Each year nearly 400, 000 people under 25 die on the world's roads, on average over 1, 000 a day. Over 90% of all road fatalities occur in low and middle-income countries, which have less than half of the world's vehicles. Road crashes cost USD $518 billion globally, costing individual countries from 1-2% of their annual GDP. Road crashes cost low and middle-income countries USD $65 billion annually, exceeding the total amount received in developmental assistance. Unless action is taken, road traffic injuries are predicted to become the fifth leading cause of death by 2030.

FIG 4: Causes of Fatal Accidents

PROBLEM DEFINITION: The above mentioned brake assist safety systems as applied to automobiles are extremely costly as they compulsorily need a computer for their implementation. More over all these systems are singular problem oriented, hence there is a need of a cost effective low end technology or device that can perform the function of alarm and brake control with minimal use of high end technology, suitable for low budget commercial vehicles. Collision warning with automatic braking system for electric cars is a technology which is cost effective and also being accurate enough to prevent collisions. Solution: The Collision warning with automatic braking system for electric cars is a answer to the above problems where in the following features have been incorporated;  Collision detection by using Ultrasonic sensor.  Collision indication using flashing LED and LCD display.  Braking using servomotor connected to rear drum brake parking cable to ensure optimal braking force and minimum braking distance.  Power cut off of the prime mover i. e. motor to avoid power loss and excessive brake wear.

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CONSTRUCTION: The Collision warning with automatic braking system for electric cars comprises of the following:

FIG 5: CIRCUIT DIAGRAM

Arduino Mega 2560: An Arduino board consists of an Atmel 8-, 16- or 32-bit AVR microcontroller with complementary components that facilitate programming and incorporation into other circuits. An important aspect of the Arduino is its standard connectors, which lets users connect the CPU board to a variety of interchangeable add-on modules known as shields. Most boards include a 5 volt linear regulator and a 16 MHz crystal oscillator, although some designs such as the LilyPad run at 8 MHz and dispense with the onboard voltage regulator due to specific form factor restrictions. An Arduino's microcontroller is also pre-programmed with a boot loader that simplifies uploading of programs to the on-chip flash memory, compared with other devices that typically need an external programmer.

FIG 6: ARDUINO MEGA 256

Collision sensing mechanism: The distance between the vehicle and obstacle is sensed using an Ultrasonic sensor. Like radar, lidar and active infrared systems, ultrasound can be used in detection and ranging applications using the time of flight principle to estimate the distance

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to an object. Ultrasonic emissions are effectively sounds waves with frequencies higher than that audible to the human ear, suitable for short to medium range applications at low speed. Ultrasonic ranging module HC - SR04 provides 2cm 400cm non-contact measurement function, the ranging accuracy can reach to 3mm. The basic principle of work: (1) Using IO trigger for at least 10us high level signal. (2) The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back. (3) IF the signal back, through high level, time of high output IO duration is the time from sending ultrasonic to returning. Test distance = (high level time× velocity of sound (340M/S) / 2.

FIG 7: ULTRASONIC SENSOR

Collision warning indicator: This is the indication or alarm system, the lamp is a red LED lamp that flashes when over speed occurs, along with LCD display, displaying the distance between the vehicle and obstacle there by alarming the driver.

FIG 8: LED’S and LCD DISPLAY Electronic Relay: Relay acts as a switch which is turned on and off using a signal. The Relay output state by a light-emitting diode. It can be controlled through the digital IO port, such as

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solenoid valves, lamps, motors and other high current or high voltage devices. Type: Digital Single relay board Rated through-current: 10A (NO) 5A (NC) Maximum switching voltage: 150VAC 24VDC Digital interface Control signal: TTL level Rated load: 8A 150VAC (NO) 10A 24VDC (NO), 5A 250VAC (NO/NC) 5A 24VDC (NO/NC) Maximum switching power: AC1200VA DC240W (NO) AC625VA DC120W (NC) Contact action time: 10ms following Module pin definitions: Pin1 - control side, Pin2 - Power supply (VCC), Pin3 – ground

FIG 9: ELECTRONIC RELAY Braking Mechanism: The brake is activated using a servo motor. An arm from the servo motor is connected to the brake pedal. When the arm of the servo motor rotates the brake pedal is actuated and the brake is applied.

FIG 10: Braking Mechanism

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WORKING MECHANISM: When the distance between the vehicle and obstacle falls below the permissible limits which is sensed by the ultrasonic sensors, the Arduino send output signal to the servo motor and the relay switch and also to the LCD display and LED flashers. The output to the servo motor is the angle through which it has to rotate and to the relay switch is to turn off the signal to it by which the device i. e. prime mover connected to it is turned off. In the LCD display the distance between the vehicles and obstacle is shown along with Red color LED flashers turned on warning the driver about the collision.

FIG 11: OBSTACLE DETECTION

SENSOR POSITIONING The position of the sensor varies according to the dimension of the vehicle. Generally for a passenger vehicle we need to use one ultrasonic sensor in the front attached to the bumper at the middle.

BRAKING: Braking of a vehicle depends upon the static friction that acts between tyres and road surface. Brakes work on the following principle to stop the vehicle: “The kinetic energy due to motion of the vehicle is dissipated in the form of heat energy due to friction between moving parts (wheel or wheel drum) and stationary parts of vehicle (brake shoes)”. The heat energy so generated due to application of brakes is dissipated into air. Brakes operate most effectively when they are applied in a manner so that wheels do not lock completely but continue to roll without slipping on the surface of road. Hydraulic brakes are commonly used in the automobiles. Principle Hydraulic brakes work on the principle of Pascal’s law which states that “pressure at a point in a fluid is equal in all directions in space”. According to this law when pressure is applied on a fluid it travels equally in all directions so that uniform braking action is applied on all four wheels.

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FIG 12: BRAKING SYSTEM

Application of Brakes: When brake pedal is pressed to apply the brakes, the piston in the master cylinder forces the brake fluid. This increases the pressure of fluid. This pressure is transmitted in all the pipes and up to all wheel cylinders according to Pascal’s law. This increased pressure forces out the two pistons in the wheel cylinders. These pistons are connected to brake shoes. So, the brake shoes expand out against brake drums. Due to friction between brake linings and drum, wheels slow down and brakes are applied. In modern cars, there are disc brakes in the front wheels and drum brakes in the rear wheels. Release of Brakes: When pedal is released, the piston of master cylinder returns to its original position due to retractor spring provided in master cylinder. Thus, fluid pressure drops to original value. The retractor spring provided in the wheel cylinders pulls the brake shoes and contact between drum and brake linings is broken. Therefore, brakes are released. Calculations: When the distance between the servo motor and obstacles is very less brakes are applied automatically. The amount of brake force generated and deceleration, stopping distance and stopping time are as follows: Assuming the following parameters for Disc Brakes: TABLE 1: BRAKE PARAMETERS Parameter Weight of the vehicle Brake Types Master cylinder bore x Stroke Brake caliper bore x no’s

Specifications 350 kgs Hydraulic disc brake on all four wheels 1”x 1. 5” 35”x 1

Collision Warning With Automatic Braking System For Electric Cars Rotor Material Rotor Diameter Brake pad area Disc Effective radius Brake fluid

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Grey Cast Iron 200mm 1920mm2 0. 083m DOT 3

The Brake force generated and the stopping distance due to the force applied on the servo motor are as follows: TABLE 2: BRAKING CALCULATIONS Parameter Force Applied on the brake pedal Braking Force Braking torque Deceleration Stopping distance Stopping time

Value 100N 1678. 34 N 98. 61 N-m 0. 4 g 14. 33m 1. 81 s

PROTOTYPE: We have made a prototype of the above system. In this we have used a dc motor instead of an electric car and a mini servo motor. The results are as follows:

FIG 13: PROTOTYPE WITHOUT OBSTACLE

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FIG 14: PROTOTYPE WITH OBSTACLE

FIG 15: LCD SHOWING DISTANCE

CONCLUSION Automatic collision warning with braking system brings major transportation benefits in terms of safety, efficiency, affordability and usability, and environment in order to achieve its development goals. It helps in decreasing the number of deaths that are occurring due to fatal accidents. Automatic collision warning with braking system is a complex large-scale control system, whose design required advances in sensor, actuator, and communication technologies and in techniques of control system synthesis and analysis. It is a measure of the advanced state of the art that these techniques have reached a stage that they could be successfully used in this project. This system is very economical when compared to the technologies being used in luxury cars. This cost effective method of collision warning along with automatic braking can be made available also to low budget cars by which there can be a tremendous decrease in the death rate due to accidents.

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