Jul 26, 2018 - SYSTEM INCORPORATE WITH ELECTRONIC BRAKE FORCE. DISTRIBUTION. Suman Bikram Bam. 020450-16. Nitu Shrestha. 020473-16.
KATHMANDU UNIVERSITY SCHOOL OF ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING
PROJECT REPORT ON
DESIGN AND FABRICATION OF ELECTROMAGNETIC BRAKING SYSTEM INCORPORATE WITH ELECTRONIC BRAKE FORCE DISTRIBUTION.
Suman Bikram Bam
020450-16
Nitu Shrestha
020473-16
Sujan Shrestha
020474-16
Nitesh Kumar Yadav
020478-16
26 July 2018
AUTHORIZATION
We hereby declare that we are the sole author of the project. We authorize the Kathmandu University to lend this thesis to other institutions or individuals for the purpose of scholarly research. We further authorize the Kathmandu University to reproduce the thesis by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research.
__________________________________ Suman Bikram Bam
Nitu Shrestha
Sujan Shrestha
Nitesh Kumar Yadav
CERTIFICATE OF APPROVAL DESIGN AND FABRICATION OF ELECTROMAGNETIC BRAKING SYSTEM INCORPORATE WITH ELECTRONIC BRAKE FORCE DISTRIBUTION. by Suman Bikram Bam Nitu Shrestha Sujan Shrestha Nitesh Kumar Yadav This is to certify that I have examined the above Project / Dissertation and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the thesis examination committee have been made.
_________________________________________ Dr. Daniel Tuladhar, PhD Associate Professor (Project Supervisor)
Er. Ashok Sapkota (Project Coordinator)
_________________________________________ Dr. Hari Prasad Neopane, PhD Head of Department
July, 2018
ACKNOWLEDGMENTS We are highly indebted to the help of our project supervisor Dr. Daniel Tuladhar, PhD, Associate Professor, Department of Mechanical Engineering, Kathmandu University. It would have been impossible to accomplish this project without his valuable help and suggestion. We wish thanks to all faculties of School of Engineering, Kathmandu University for providing support during the project period. We wish thanks to all classmates and staff of SOE who helped us to carry out this project. Finally, we want to express our heartily thanks to all those who directly or indirectly provided us their cooperation in the completion of this project. At last but not the least, we also have high sense of appreciation to our own project group for a unit co-ordination among the group during the project work.
Team Members Suman Bikram Bam Nitu Shrestha Sujan Shrestha Nitesh Kumar Yadav.
i
TABLE OF CONTENTS ACKNOWLEDGMENTS………………………………………………………......i TABLE OF CONTENTS…………………………………………………………..ii LIST OF FIGURES………………………………………………………………..iv LIST OF TABLES…………………………………………………………………v ABSTRACT……………………………………………………………………….vi LIST OF ABBREVIATIONS…………………………………………………….vii LIST OF SYMBOLS…………………………………………………………….viii CHAPTER 1 INTROUCTION……………………………………………………..1 1.1 Background……………………………………………………………………1 1.2 Literature Review……………………………………………………………..3 1.3 Principle of Braking System…………………………………………………..3 1.4 Principle of Electronic Brakeforce Distribution………………………………4 1.5 History………………………………………………………………………...5 1.6 Types of Braking System……………………………………………………..5 1.6.1 Mechanical Brakes………………………………………………………..6 a. Disc Brakes…………………………………………………………………6 b. Drum Brakes………………………………………………………………..6 c. Hydraulic Brakes…………………………………………………………...6 d. Power Brakes……………………………………………………………….6 1.7 Objectives……………………………………………………………………..7 1.7.1 Primary Objectives.……………………………………………………….7 1.7.2 Secondary Objectives……………………………………………………..7 1.8 Significance/Scope……………………………………………………………7 1.9 Limitations…………………………………………………………………….7 CHAPTER 2 METHODOLOGY…………………………………………………..8 2.1 Theoretical/Conceptual Framework…………………………………………..8 2.2 Study Design and Component Description…………………………………...8 2.2.1 Driving Unit……………………………………………………………….9 a. Wheel……………………………………………………………………….9 b. Motor……………………………………………………………………….9 c. Power Control………………………………………………………………9 2.2.2 Braking Unit……………………………………………………………..10 a. Electromagnet……………………………………………………………..10 b. Brake shoe………………………………………………………………...10 c. Spring……………………………………………………………………...10 d. Wooden Wheel……………………………………………………………10 2.2.3 Sensor unit……………………………………………………………….11 a. Load Cell………………………………………………………………….11 b. Hall Effect Sensor…………………………………………………………11
ii
2.2.4 Electronic Control Unit…………………………….……..………………12 a. Arduino…………………………………………….………..…………….12 b. HX711 Amplifier………………………………….…………..…………..12 c. Relay Switch……………………………………….………….…………..13 d. LCD Display……………………………………….………….…………..13 2.3 Calculation…………………………………………….………….………….14 2.4 Working Mechanism………………………………….……………………..17 2.5 Observation Table…………………………………….……………………..19 2.6 Code…………………………………………………….……………………21 2.6.1 Code for Measurement of RPM of wheel………….……………………21 2.6.2 Code for Load Cell and Electronic Control Unit…….…………………..22 2.6.3 Code for Load Cell Amplifier…………………………………………...23 2.7 Gantt Chart…………………………………………………………………..27 CHAPTER 3 DESIGN……………………………………………………………28 CHAPTER 4 DISCUSSION……………………………………………………...29 4.1 Work…………………………………………………………………………29 4.2 Problem Encountered…………………………………………………...…...29 CHAPTER 5 Budget Estimation………………………………………………….30 CHAPTER 6 EXPECTED OUTCOMES………………………………………...31 CHAPTER 7 CONCLUSION…………………………………………………….32 REFERENCES……………………………………………………………………33
iii
LIST OF FIGURES Figure 1.1 Graph of vehicle without and with EBD………………………………..2 Figure 1.2 Working Principle of Electromagnetism………………………………..3 Figure 1.4 Vehicle with and without EBD…………………………………………4 Figure 2.4 Flowchart showing the working steps of our prototype model………..18 Figure 3.1 Isometric Drawing of our model………………………………………28
iv
LIST OF TABLES Table 2.4.1 Stoppage Distance for Deal load only when EBD is off……………..19 Table 2.4.2 Stoppage Distance for Dead Load only when EBD is on……………19 Table 2.4.3 Stoppage Distance for Maximum load when EBD is off…………….20 Table 2.4.4 Stoppage Distance for Maximum load when EBD is on……………..20 Table 5.1 Total Budget Estimation………………………………………………..31
v
ABSTRACT This project mainly focuses on the analysis and design of Electromagnetic Brakes when coupled with Electronic Brake force distributer and is entitled as, “Design and Fabrication of Electromagnetic Braking System Incorporate with Electronic Brake Force Distribution.” The objective of our project is to come up with a Electronic Braking System with EBD prototype that can be operate by the help of microcontroller to provide appropriate amount of brake force the brakes automatically at the instance required without driver input. EBD are till now being employed in vehicles with ABS nowadays to prevent the accidents. Electromagnetic brakes are used to apply the brakes automatically. Microcontroller is used to control the motion of brakes and motor at the time of braking. Microcontroller gets signal about the distribution of load over the vehicle and provides required amount of braking force to rear and front wheels resulting in effective and efficient braking. The aim of making this type of braking system with EBD is to check how EBD reacts when combined with Electromagnetic brakes and prevent the possible effects of accidents caused due to insufficient amount of brake force required to stop vehicle. It is anticipated that this will be an efficient system if tested successfully in automobiles, helping to prevent the loss of life and property. Keyword: Electromagnetism, Brake Force, EBD.
vi
LIST OF ABBREVIATIONS AC ABS DC EBD EBL ECU EM GND KE LCD RPM
Alternating Current Anti-Locking Braking System Direct Current Electronic Brake Force Distribution Electronic Brake Force Limitation Electronic Control Unit Electro-Mechanical Ground Kinetic Energy Liquid Crystal Display Revolution Per Minute
vii
LIST OF SYMBOLS A
Cross sectional area
[L2]
B
Magnetic field
[T]
F
Force
[MLT-2]
g
Acceleration due to gravity
[LT-2]
I
Current
[A]
R
Resistance
[ML2T-3I-2]
V
Voltage
[ML2T-3I-1]
W
Power
[ML2T-3]
ɳ
Efficiency
μ
Magnetic permeability
[MLT-2I-2]
ρ
Electric Conductance
[M-1L-2T3I2]
viii
CHAPTER 1 INTRODUCTION 1.1 Background A brake is a device which inhibits motion. Its opposite component is a clutch. Most commonly brakes use friction to convert kinetic energy into heat, though other methods of energy conversion may be employed. The principle of braking in road vehicles involves the conversion of kinetic energy into thermal energy (heat). When stepping on the brakes, the driver commands a stopping force several times as powerful as the force that puts the car in motion and dissipates the associated kinetic energy as heat. Brakes must be able to arrest the speed of a vehicle in a short periods of time regardless how fast the speed is. As a result, the brakes are required to have the ability to generating high torque and absorbing energy at extremely high rates for short periods of time. Brakes may be applied for a prolonged periods of time in some applications such as a heavy vehicle descending a long gradient at high speed. Brakes have to have the mechanism to keep the heat absorption capability for prolonged periods of time. Electromagnetic brakes (also called electro-mechanical brakes or EM brakes) slow or stop motion using electromagnetic force to apply mechanical resistance (friction). Since becoming popular in the mid-20th century especially in trains and trams, the variety of applications and brake designs has increased dramatically, but the basic operation remains the same. Electromagnetic brakes have been used as supplementary retardation equipment in addition to the regular friction brakes on heavy vehicles. Electromagnetic brakes are the brakes working on the electric power & magnetic power. They works on the principle of electromagnetism. The working principle of this system is that when the magnetic flux passes through and perpendicular to the rotating wheel the eddy current flows opposite to the rotating wheel/rotor direction. This eddy current trying to stop the rotating wheel or rotor. This results in the rotating wheel or rotor comes to rest/ neutral.[1] Electronic brake force distribution (EBD or EBFD) or electronic brake force limitation (EBL) is an automobile brake technology that automatically varies the amount of force applied to each of a vehicle's wheels, based on road conditions, speed, loading, etc. EBD is an active vehicle safety feature designed to make braking as efficient as possible. EBD prevents wheel from locking under various driving condition by regulating brake pressure. This is because the car will have less braking distance or maximum deceleration when both wheels retard at same rate, this is where EBD kicks in by applying right pressure to each wheel. EBFD reduces these dangers by automatically balancing the brake force applied to each wheel according to the overall weight distribution of the vehicle.[2] 1
Electromagnetic brakes when coupled with electronic brake force distribution(EBD) help us in swift driving as it satisfy all the energy requirement of braking without the use of friction, reduce slip ratio on the tyres. EBD helps to distribute the brake force equally on both front and rear wheel which results in effective braking that reduce the risk of fishtailing, spinning, over steering, and understeering. A special function of antilock braking systems (ABS), EBFD makes the amount of brake force applied to a wheel proportional to that wheel’s load at the time. [5]
Fig 1.1: Vehicle without and with EBD.[6]
2
1.2 Literature Review This chapter presents an overview of previous work on related topics that provide the necessary background for the purpose of this project. The literature review concentrates on a range of braking system topics and EBD. For the understanding of braking capacity, a review of literature is required in experimental testing, current design practice, theoretical strength evaluation and modeling techniques such as ANSYS. The literature review begins with a coverage of general braking system used, which serves to set the context of the project. Following are the few topics we reviewed during our project work. 1.3 Principle of Braking System. The principle of braking in road vehicles involves the conversion of kinetic energy into thermal energy (heat). When stepping on the brakes, the driver commands a stopping force several times as powerful as the force that puts the car in motion and dissipates the associated kinetic energy as heat. Brakes must be able to arrest the speed of a vehicle in a short periods of time regardless how fast the speed is. As a result, the brakes are required to have the ability to generating high torque and absorbing energy at extremely high rates for short periods of time. Brakes may be applied for a prolonged periods of time in some applications such as a heavy vehicle descending a long gradient at high speed. Brakes have to have the mechanism to keep the heat absorption capability for prolonged periods of time. Electromagnetic Braking system works on the principle of electromagnetism.[1]
Fig 1.2: Working Principle of Electromagnetism
3
1.4 Principle of Electronic Brake Force Distribution. EBD distributes the necessary amount of brake force required for effective braking. According to the weight distribution over the vehicle except dead load, it provides necessary brake force to each brake. Under no load condition, small brake force is provided to rear wheel and when loads i.e passengers and their luggage is added, then for vehicle to stop at safest distance in emergency braking, it is required to provide rear wheel greater brake force which is provided by EBD.
Fig 1.4: Vehicle without and with EBD.[6]
4
1.5 History It is found that electromagnetic brakes can develop a negative power which represents nearly twice the maximum power output of a typical engine, and at least three times the braking power of an exhaust brake (Reverdin 1994). These performance of electromagnetic brakes make them much more competitive candidate for alternative retardation equipment’s compared with other retarders. By using by using the electromagnetic brakes are supplementary retardation equipment, the friction brakes can be used less frequently, and therefore practically never reach high temperatures. The brake linings would last considerably longer before requiring maintenance and the potentially brake fade problem could be avoided. In research conducted by a truck manufacturer, it was proved that the electromagnetic brake assumed 80% of the duty which would otherwise have been demanded of the regular service brake (Reverdin 1974). The installation of an electromagnetic brake is not very difficult if there is enough space between the gearbox and the rear axle. If did not need a subsidiary cooling system. Electronic brake force distribution (EBFD) is a braking system that monitors factors like vehicle weight and road condition and adjusts the vehicle's braking force accordingly. Some vehicle manufacturers provide EBFD as a standard feature. EBD has been used in some vehicles with anti-locking braking system(ABS) but some test have been conducted with EM brakes and it has not been installed for commercial use.
1.6 Types of Braking System Brakes can be broadly classified into following types; Mechanical brakes Disc brake Drum brake Hydraulic Brakes Power Brakes Air brake Air Hydraulic brake Vacuum brakes Electro-mechanical brake or electric brake
5
1.6.1 MECHANICAL BRAKES a) Disc Brake It is a type of brake that uses calipers to squeeze pair of pads against disc or rotor which is attached to the wheel by creating frictional force between them and retards the motion of rotating shaft connected to it. A disc brake work on the principle of transmission of fluid pressure. This law states that,” the pressure exerted anywhere in a confined incompressible fluid is transmitted in all directions throughout the fluid such that the pressure ratio remains same.”
b) Drum Brakes A drum brake is that brake which uses friction caused by set of shoes or pads that press outward against a rotating cylinder part called as brake drum. It is commonly used in vehicles where high amount of brake force is required like heavy duty vehicles, medium vehicles, etc. c) Hydraulic Brakes A hydraulic braking system is piston cylinder arrangement consisting of incompressible fluid typically glycol ethers or diethylene glycol which multiplies force significantly. It works on Pascal’s law and transfers hydraulic pressure. d)
Power Brakes Air brakes Air hydraulic brakes Vacuum brakes Electro-mechanical brakes
6
1.7 Objectives 1.7.1 Primary Objectives To design and fabricate EM brake for four wheeler and ensure equal distribution of brake force when load is distributed over the vehicle.
1.7.2 Secondary Objectives To analyze the braking efficiency in no load and when additional load is placed on the vehicle. To check the compatibility of EBD with EM brakes in four vehicles. To study about different braking system used in automobiles and its design. To learn Arduino programming to operate high voltage DC circuits. To learn to operate different sensors. 1.8 Significance/Scope EM brakes are already in use under some railway system. EM brakes are equally applicable to heavy and light vehicles. EBD can deduce the car from the slip ratio of the wheels and compensate accordingly in icy or watery roads. When a truck with heavy loads apply brakes EBD becomes aware of it through its effect on the slip ratio of the tires and distributes equal amount of brake force to all wheels. Heavy braking will be more comfortable: since braking is more effective with EBFD, your vehicle will stop faster.
1.9 Limitations The installation of an electromagnetic brake is very difficult if there is not enough space between the gearbox and the rear axle. Due to residual magnetism present in electromagnets, the brake shoe takes time to come back to its original position. EBFD cannot warn of impending collisions or of bad road conditions, so it is up to us to assess road conditions and notice any potential hazards.
7
CHAPTER 2 METHODOLOGY 2.1 Theoretical/Conceptual Framework EBD till now have been coupled with only Anti-locking Braking System, so our project focuses on the behavior of EBD when coupled with Electromagnetic Braking System. When this system is made to run on road it is nearly impossible to see the result of changing braking force in this project due to its small size and lack of precise instrument to notice the slight change in effect of braking nature so whole system was be mounted over a frame and thus test run were conducted by placing different loads and analyzing thus result given by ECU. Multiple loads was placed which helped us to study about the changing magnetic power of rear and front brakes under different conditions. These conditions include; 1. Live and dead load on vehicle which acts unchanged once placed, 2. In case of emergency braking, some percentage of load is transferred from rear to front wheels. These conditions and weight distribution was automatically detected by microcontroller and it calculated according to predefined set of rules and algorithm, appropriate amount of brake force needed to each part of vehicle and distributes the amount of current from power source accordingly which ultimately results in safe and short and efficient braking.
2.2 Study Design and Component Description Our project is divided into four different parts; 1. Driving Unit 2. Braking Unit 3. Sensor Unit 4. Electronic Control Unit
8
2.2.1 Driving Unit a. Wheel Wheels are one of the important part of a vehicle which is a medium to transfer the force to the ground that makes the vehicle move. In our prototype, the rear wheels are driven by motor. We have used two sets of wheels of different diameters. Larger wheel of diameter 95mm and smaller with diameter 69mm.
Fig 2.2.1: Wheel
b. Motor We have selected 30-40V maximum rating DC motor for our project which gives the required power and velocity output.
Fig: 2.2.2 DC Motor c. Power Control This division consists of power supply to whole system and a separate power control system to control the motion of motion.
9
2.2.2 Braking Unit a. Electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. Electromagnets usually consist of insulated wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole in the center of the coil. The wire turns are often wound around a magnetic core.
Fig 2.2.2.a Electromagnet b. Brake Shoe It is part that will stop the main wheel when the electromagnet is turned on. c. Spring A coil spring, also known as a helical spring, is a mechanical device which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. Two compression springs are used to push back the brake shoe back in its position. d. Wooden Wheel This is used as stopping wheel. When electromagnet is turned on it attract the plunger placed inside electromagnet and stops the wooden wheel attached to the rotating wheel.
10
2.2.3 Sensor Unit a. Load Cell A load cell is a transducer that is used to create an electrical signal whose magnitude is directly proportional to the force being measured. The various load cell types include hydraulic, pneumatic, and strain gauge. The Weight sensor also known as load cell is made up of aluminum – alloy designed to measure force in one direction. It ignores other force applied while is measure the specific force. It is applicable mostly for measuring human body weight. It required a load cell amplifier such as a HX711 load cell amplifier, or spark fun open scale or 1046 Phidget Bridge for electrical signal output.
Fig 2.2.3.a: Load Cell
b. Hall Effect Sensor It can be used as speed sensing and current detection of electromagnets of producing magnetic fields. We have used it to measure the rpm of wheel and strength of electromagnet.
Fig 2.2.3.b: Hall Effect Sensor
11
2.2.4 Electronic Control Unit a. Arduino Arduino Uno type of Arduino board is used which is most common type. The Uno board is powered via the USB connection or with an external power supply. The power source is selected automatically. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the GND and Vin pin headers of the POWER connector.The board can operate on an external supply from 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may become unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.
Fig 2.2.4.a: Arduino
b. HX711 Amplifier The HX711 load cell amplifier is used to get measurable data out from a load cell and strain gauge.
Fig 2.2.4.b: HX711 load cell amplifier
12
c. Relay Switch A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal. In this project, we have connected this relay switch with electromagnets and it operates normally on and normally off for both pair of rear electromagnets.
Fig 2.2.4.c: 12V Relay Switch d. LCD Display Here, we have used 16*2 LCD display as supplementary display unit of results. It is also connected with serial monitor of arduino.
Fig 2.2.4.d: LCD Display
13
2.3 Calculations Mass of system = 1 kg (only dead load considered), 30-40V DC Motor. (2.3mm shaft diameter, 2pin connection) Speed of Motor: 6000 RPM Pulley Reduction Ratio: 1:1 Force Produced: The force between electromagnet and another piece of ferromagnetic material separated by a gap of distance g is,
Where:
= 4π*10^-7 F is the force in Newtons N is the number of turns I is the current in Amps A is the area in length units squared g is the length of the gap between the solenoid and a piece of metal.
Note, any units can be used for A and g so long as they are consistent. NOTE: These Calculations is done when ECU is switched off .When ECU is switched on these values will be divided proportionally to each brakes. 1.Magnetic force produced, B’ μ IN =4π*10⁻⁷*4*800 =4.02*10⁻3 T which is magnetic force produced by one electromagnet as we are using two electromagnets so our total force will be Total Magnetic force produced in either rear or front brakes
B=2*B’ =8.04*10⁻3 T.
14
2. Total Force produced, F= (N*I)2 μ0 A / (2 g2) F=161.7 N 3.Resistance of wire, R=ρL/A =1.7*10⁻⁸ *13.8/0.503 =0.466 Ω 4.Heat produced, H=I2RT =4*4*0.466*60 =112 J 5. Power transmitted by the motor, P = 20 W 6. The twisting moment (T’), T’ = P*60/2πN =1.90 N.m #Shafts Subjected to Twisting Moment Only T’/J = τ/r for round solid shaft, polar moment of inertia, J = πd⁴ /32, So above equation becomes, T’ =πτd3/16, d =3 mm. Solid shaft of mild steel was used. Considering factor of safety, shaft of 7mm is used. 7. Kinetic energy of vehicle during braking is given by, KE=1/2*m*(U2-V2) =0.5*1*(102-02) =50 J
15
8. Maximum weight transferred from rear to front wheels on applying brakes, Condition: Wheel base equal to 3 times the height of its CG above the ground and adhesion factor of road is 0.6. W=µ’*h*f*w/(b*g), =(0.6*0.6)*w/3 =12w Therefore weight transfer= 12%. 9. Minimum Stoppage Distance When vehicle deaccelerate with g=9.8 m/s2, S=U2/2g =10^2/2*9.8 S=5.1m 10. Average Braking Force to stop vehicle, Work done to stop vehicle = Change in it’s KE FS =0.5MU2 F=0.5*20*102/5.1 F’=200 N
Since theoretically calculated force produced by electromagnets (F) is less than force required to stop the vehicle in 5.1 m so vehicle will stop at 6.2m. 11. Braking Efficiency ɳ=0.4U2/S =0.4*102/5.1 ɳ=80.1 % NOTE: The value of efficiency changes for each velocity and respective stoppage distance.
16
2.4 Working Mechanism The prototype is powered by a DC motor which gets power source from DC supply of 12V capacity. The motor runs the prototype. Front and rear shafts is connected by rubber chain. Rear shaft is directly connected to the motor with 1:1 pulley reduction ratio and both shafts rotates at the same speed. Load cell are fixed to detect the presence of weight distribution over the vehicle. The signal from the sensors is interpreted by the microcontroller which controls the motor and electromagnetic brakes. When there is no load distribution over the vehicle, small amount of force in rear wheel can also help in effective braking. In our prototype, when there is no load then current is distributed among the electromagnets in the ratio of 5.5: 4.5. In case of detection of external load on vehicle except dead load of vehicle, the microcontroller activates the electromagnetic brakes with current ratio of 7:3 and at the same time stops the motor stopping the motion of prototype. This variable action of current is successfully carried out with the help of set of resistor of 10 Ω and 13 Ω controlled by a 12V relay working on normally on and normally off conditions. This varying brake force results in changing stopping distance. Even when loaded with extra weight running at maximum velocity i.e. maximum momentum of prototype when achieved, due to presence of EBD, it have possible short stopping distance and is further shown below in flow chart and tables.
17
Vehicle Starts
Sensors sense weight distribution
Weight Distribution
Rear
Yes
Front
No
Distribute current into 7:3
Divide current into 5.5:4.5
Apply Brakes and vehicles stops .
Fig 2.4: Flowchart showing the working steps of our prototype model.
18
2.5 Observation Table On testing phase of our prototype, we considered the following cases; a. For Dead load (EBD on/off) b. For maximum load (EBD on/off) We know, Linear velocity (v)= angular velocity (w) * radius of rotating circle Or, v= (2ℿr*RPM)/60 v= 4.97*10-3 *RPM a. For Dead Load only (1 kg) S.N Initial Velocity Final (m/s) (m/s) 1. 2. 3.
0.2485 0.5467 0.6958
0 0 0
Velocity Time to Distance stop (sec) Covered (m) 0.9 0.2235 1.2 0.65604 1.3 0.90454
Condition of EBD Off Off Off
Table 2.4.1: Stoppage distance for dead load only when EBD is switched off
S.N Initial (m/s) 1. 2. 3.
0.3479 0.4473 0.5964
Velocity Final (m/s) 0 0 0
Velocity Time to Distance stop (sec) Covered (m) 1.0 0.3479 1.2 0.53676 1.4 0.83496
Condition of EBD On On On
Table 2.4.2: Stoppage distance for dead load only when EBD is switched on
19
b. For Maximum load (20 kg) S.N Initial (m/s) 1. 2. 3.
0.2982 0.4473 0.6561
Velocity Final (m/s) 0 0 0
Velocity Time to Distance stop (sec) Covered (m) 0.9 0.26838 1.1 0.49203 1.3 0.83993
Condition of EBD Off Off Off
Table 2.4.3: Stoppage distance for maximum load when EBD is switched off
S.N Initial (m/s) 1. 2. 3.
0.2485 0.4970 0.7455
Velocity Final (m/s) 0 0 0
Velocity Time to Distance stop (sec) Covered (m) 0.9 0.22365 1.1 0.5467 1.4 1.0437
Condition of EBD On On On
Table 2.4.4: Stoppage distance for maximum load when EBD is switched on
20
2.6 CODE 2.6.1 Code for measurement of RPM of wheel // Hall effect sensor int hallsensor = 2; volatile byte counter; unsigned int rpm; unsigned long passedtime; void isr() { counter++; } void setup() { Serial.begin(9600); attachInterrupt(0, isr, RISING); pinMode(hallsensor, INPUT); counter = 0; rpm = 0; passedtime = 0; } void loop() { delay(1000); detachInterrupt(0); rpm = 60*1000/(millis() - passedtime)*counter; passedtime = millis(); counter = 0; Serial.print("RPM="); Serial.println(rpm); attachInterrupt(0, isr, RISING); }
21
2.6.2 Code for Load Cell and ECU #include "HX711.h" #define DOUT 3 #define CLK 2 HX711 scale(DOUT, CLK); float calibration_factor = 50000; int relay=A0; void setup() { pinMode(relay,OUTPUT); Serial.begin(9600); Serial.println("Press T to tare"); scale.set_scale(96650); scale.tare(); } void loop() { Serial.print("Weight of object: "); Serial.print(scale.get_units(), 3); Serial.println(" kg"); if(Serial.available()) { char temp = Serial.read(); if(temp == 't' || temp == 'T') scale.tare(); } if(scale.get_units() >= 1) { digitalWrite(relay,HIGH); Serial.print(“Brake Force is distributed in the ratio of 5.5:4.5 among the front and rear wheels”); }
22
else { digitalWrite(relay,LOW); Serial.print(“Brake is distributed in the ration of 7:3 among front and rear wheels”); } }
2.6.3 Code for Load Cell Amplifier #include #include "HX711.h" #if ARDUINO_VERSION
