Chapter 1 Introduction
The demand for higher efficiency from the automobile vehicle and their associated accessories has increased in last few years due to the continuous increase in fuel price, increased pollution rate due to emission from vehicle. It is common practice to use high grade fuel, efficient transmission system, braking system, aero foil design and modified engine design to increase efficiency, life of vehicle and decrease pollution rate. In the last few years, due to updating the technology economy of vehicle has raised.
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For hybrid vehicle and locomotives regenerative braking system technology is considered to be one of the most advanced technologies which expected to have good contribution into automobile and environment improvements. Hybrid vehicle and locomotives have efficient transmission, higher mechanical efficiency etc. by using the different advanced technologies like regenerative braking system.
Generally in automobiles whenever the brakes are applied the vehicle comes to the rest and the kinetic energy gets wasted due to friction due to braking. Using regenerative braking system in automobiles it enables us to recover the kinetic energy of the vehicle to some extent that is lost during braking.
This technology of regenerative braking controls the speed of the vehicle by converting the portion of the vehicle’s kinetic energy into another useful form of energy. The energy produced could be stored as electrical energy in the automobile battery or as mechanical energy in flywheels, which can be again used by the vehicle.
Regenerative braking is one of the emerging technologies which can prove very beneficial. The use of regenerative braking system in a vehicle not only results in the recovery of the energy but it also increases the efficiency of the vehicle and save energy which is stored in battery.
Regenerative braking system has wide scope for further development and energy savings. The use of more efficient systems could lead to huge saving in the economy of any country.
In the automobile vehicle many accessories and mountings, such as braking system, power transmission system, radiator, gear box, engine components, tires, flywheel etc. are used. Parts like braking system, engine components and transmission system in which heat loss occurs. To increase
overall efficiency of the vehicle heat loss must be reduced and this can be achieved by different techniques. Regenerative braking is one of them which reduce heat loss in braking and recover the kinetic energy of the vehicle.
1.1 Introduction to brakes
1.1.1 Principle of brake
It goes without saying that brakes are one of the most important control components of vehicle. They are required to stop the vehicle within the smallest possible distance and this is done by converting the kinetic energy of the vehicle into the heat energy which is dissipated into the atmosphere.
1.1.2 Requirements of braking
Following are the main requirements of braking
It must be strong enough to stop the vehicle within a minimum distance in an emergency. But this should also be consistent with safety. The driver must have proper control over the vehicle during emergency braking and the vehicle must not skid.
The brakes must have good anti-fade characteristics i.e. their effectiveness should not decrease with constant prolonged application for example, while descending hills. These requirements demand that cooling of brakes should be very efficient.
1.2 Types of brakes
Following types of brakes used in automobile.
There are mainly four types of brakes.
Mechanical brakes
Hydraulic brakes
Pneumatic or Air brakes
Electromagnetic brakes
1.2.1 Mechanical brakes
Disc Brake
As shown in figure the disc brake consists of a cast iron disc bolted to the wheel hub and the stationary housing called caliper. The caliper is connected to some stationary part of the vehicle, like the axle casing or the hub axle and is cast in two parts containing a piston.
(a) (b )
Figure 1: Disc Brake
When the brakes are applied, hydraulically actuated pistons move the friction pads into contact with disc, applying equal and opposite forces on the later. On releasing the brakes, the rubber sealing rings act as return springs and retract the pistons and the friction pads away from the disc.
For a brake of this type,
T = 2µpaR
Where, µ = co efficient of friction p
= fluid pressure
a = cross-sectional area of one piston
R = distance of the longitudinal axis of the piston from the wheel
2. Drum Brake
Figure 2: Drum Brake
A brake drum is attached concentric to the axle hub whereas in the axle casing is mounted a back plate. In case of front axle, the brakes plate is bolted to the steering knuckle.
The back plate is made of pressed steel sheet and is ribbed to increase rigidity and to provide support to expander, anchor, and brake shoes. It also protects the drum and shoe assembly from mud and dust. Moreover, it absorbs the complete torque reaction of the shoes due to which reason it is sometimes also called „Torque plate?.
Friction linings are mounted on the brake shoes. One or two reactor springs are used which serve to keep the brakes are not applied. The brake shoes are anchored at one end, whereas on the other ends force F is applied by means of some brake actuating mechanism, which forces the brake shoe against the revolving drum, thereby applying the
brakes.
1.2.2 Hydraulic Brakes
Figure 3: Hydraulic Brake System
Most of the cars today used hydraulically operated foot brakes on all the four wheels with which an additional hand brake mechanically operated on the rear wheels. An outline of the hydraulic braking system is shown in figure. The main component in this is the master cylinder, which contains reservoir for the brake fluid. Master cylinder is operated by the brake pedal and is further connected to the wheel cylinders in each wheel through steel pipe lines, unions and flexible hoses.
The system is so designed that even when the brakes are in the release position, a small pressure of about 50 kPa is maintained in the pipe lines to ensure that the cups of the wheel cylinder are kept expanded.
1.2.3 Pneumatic Brakes
The operation of air brake is similar to the hydraulic brake except that in their case compressed air is used to apply the brakes instead of hydraulic pressure. Air brakes are commonly used on heavy vehicles, like trucks, buses, etc.
The complete layout circuit is shown in figure. Compressor takes air from the atmosphere through the filter and compressed air is sent to the reservoir through the unloader valve, which gets lifted at a pre-determined reservoir pressure (about 900 kPa) and relieves the compressor of the load.
From the reservoir air goes to the brake chamber also called the diaphragm units at each wheel, through the brake valve. When the brakes are applied, the air pressure in the reservoir decreases when the pressure drops to approximately 700 kPa, the governor again cuts in the compressor to raise system pressure. In case the air system pressure falls to about 400 kPa, a warning usually in the form of buzzer is sounded.
1.2.4 Electromagnetic Brakes
These brakes are mostly used where an electric motor is already part of the automobile vehicle. Many hybrid gasoline or electric vehicles use the electric motor as a generator to charge electric batteries and also used as a regenerative brake in this type of vehicle used electromagnetic brakes.
Some diesel or electric railroad locomotives use the electric motors to generate electricity which is given to a resistor bank and dissipated as heat. Some vehicles, such as some transit buses, do not already have an electric motor but use an auxiliary “retarder” brake that is effectively a generator with an internal short-circuit.
Similar types of such a brake are eddy current brakes, and electro-mechanical brakes (which actually are magnetically driven friction brakes, but nowadays are often just called
“electromagnetic brakes” as well.
1.3 Characteristics of braking system
Brakes having the following characteristics including
Peak force – The peak force is the maximum decelerating effect that can be achieved. It is more than the traction limit of the tires, in which case the brake can cause a wheel to skid.
Continuous power dissipation – when the brakes are applied, brake pads become hot due to friction, and fail when the temperature gets too high. The maximum amount of power that can be dumped through the brake without failure is the continuous power dissipation. Constant power dissipation often depends on the temperature and speed of natural cooling air.
Fade – When the brake material becomes hot, it may become less effective, called brake fade. Some designs are inherently prone to fade, while other designs are relatively less effective. Further, use considerations, such as cooling, often have a big effect on fade.
Smoothness – A brake that has geometrical irregularities such as grabby, pulses, has chatter, or otherwise exerts varying brake force may lead to slip of wheels. For example, railroad wheels have little traction, and friction brakes without an anti-skid mechanism often lead to skids, which increases maintenance costs and leads to a “thump thump” feeling for passengers.
Power – Brakes are considered as “powerful” when a small human application force leads to a braking force that is higher than average for other brakes in the same class. The word
“powerful” does not relate to continuous power dissipation, and may be confusing in that a brake may be “powerful” and brake strongly with a gentle brake application, yet have worse peak force than a less “powerful” brake.
Pedal feel – Brake pedal feel consist of subjective perception of brake power output as a function of pedal travel. Pedal travel is affected by the fluid displacement of the brake and other factors.
Drag – Brakes have varied amount of drag in the off-brake condition depending on design of the system to accommodate total system compliance and deformation that exists under braking with ability to retract friction material from the rubbing surface in the offbrake condition.
Durability – Friction brakes have wear surfaces that must be changed regularly. Wear surfaces include the brake shoes or pads, and also the brake disc or drum
Weight – Brakes are often “added weight” in that they serve no other function. Further, brakes are often mounted on wheels, and un-sprang weight can significantly act traction in some circumstances. “Weight” may mean the brake itself, or may include additional support structure
Noise – Brakes usually create some noise when applied, but often create squeal or grinding noises that are too loud.
1.4 Introduction of Regenerative Braking System
Regenerative Braking System is the totally different approach from the conventional braking. In the regenerative braking system kinetic energy is nod wasted in the form of heat energy.
Following is the History of the Regenerative Braking System.
1.4.1 History
In 1908 C.J. Paulson patented a smart car with Regenerative Braking System.
The “Energy Regeneration Brake” system was developed in 1967 by American Motors Corporation (AMC) in cooperation with Gulton Industries.
The Energy Regeneration from braking idea was later commercialized by the Japanese and both Ford ;Chevrolet licensed it from the Toyota for use in their domestic built hybrid Vehicles.
During the late 2000s,an electronic control unit used by BMW that engages the alternator during braking.
1.4.2 Definition of Regenerative Braking System
Regenerative braking means re-capturing the kinetic energy of the vehicle’s motion and turning it into another type of energy.
Chart 1: Kinetic Energy V/S Speed with Different Loads
Graph shows the relation of kinetic energy in N-m with the speed in kph. The kinetic energy of vehicle can be calculated by following equation.
K=
In the conventional brake this kinetic energy is wasted during braking a vehicle but in case of regenerative braking most of the kinetic energy is recovered and utilize it in different form.
1.4.3 Need of Regenerative Braking System
Regenerative braking has the potential to improve the fuel economy of vehicles.
The price increase of petroleum based fuel also given rise to various research and development efforts in energy conservation.
It reduces the emission of the vehicles.
To get batter passenger comfort by good and stable transient response of braking force.
1.4.4 Working of Regenerative Braking System
When a vehicle is running on the road, vehicle has kinetic energy, which is simply defined as the energy something possesses because it is in motion. When we apply the brakes, kinetic energy of vehicle dissipate as heat in case of conventional friction type brakes but in case of regenerative braking systems use their electric motors to slow down the car and generate electrical energy (hybrids still have conventional friction brake systems that are used at higher deceleration rates).In Hybrid vehicles regenerative brakes are the most common, and electric vehicles can reverse the flow of power through their electric motors backwards to slow down the vehicle.
In one of those disciplines of engineering coincidences, electric generators are the same as electric motors. When we apply a current to a motor it turns and converts electric energy into mechanical torque and when we apply a mechanical torque to the motor it induces electric current so it can be used as a generator. By using this phenomenon we can convert the kinetic energy in to the electric energy. Use this collected energy into the battery and, the next time we step on the accelerator, some of the energy we just saved is used to get motion of car and it can also use in electric equipment. We can store the energy in form of kinetic energy by using auxiliary flywheel.
1.5 Methods of Regenerative Braking
Following are the methods of regenerative braking
1) By using Battery storage
By using Flywheel storage
By using Hydraulic storage
1.5.1 Battery Storage Regenerative Braking
Regenerative braking is used in vehicles that make use of electric motors, primarily fully electric vehicles and hybrid electric vehicles. It’s run in one direction; it converts electrical energy into mechanical energy.
Figure 4: RBS by Using Battery Storage System
When the motor is run in the opposite direction, a properly designed motor becomes an electric generator, converting mechanical energy into electrical energy. This electrical energy can then be fed into a charging system for the car’s batteries.
1.5.2 Flywheel storage Regenerative Braking
In this system, the translational energy of the vehicle is transferred into rotational energy in the flywheel, which stores the energy until it is needed to accelerate the vehicle.
The benefit of using flywheel technology is that more of the forward inertial energy of the car can be engaged even during relatively short intervals of braking and acceleration. In the case of the batteries, they are not able to accept charge at these rapid intervals, and thus more energy is lost to friction.
1.5.3 Hydraulic Storage Regenerative Braking
To improve the vehicle fuel economy an alternative regenerative braking system is being developed by the Ford Motor Company and the Eaton Corporation. It is called Hydraulic Power Assist or HPA
In this system when the driver steps on the brake, the vehicle?s Kinetic energy is used to power a Reversible pump.
This Reversible Pump sends hydraulic fluid from a low pressure accumulator inside the vehicle into a high pressure accumulator. This slow the vehicle and helps bring it to stop
The fluid remains under pressure in the accumulator, until the driver pushes the accelerator again.
Figure 5: Hydraulic Storage Regenerative Braking
During braking, the vehicle?s Kinetic energy drives the pump transferring hydraulic fluid from the low pressure reservoir to the high pressure accumulator. The fluid compresses the nitrogen gas in the accumulator and pressurizes the system.
During acceleration, fluid in high pressure accumulator is metered out to drive the pump as a motor. The system propels the vehicle by transmitting torque to the driveshaft.
1.6 Potential Savings due to Regenerative Braking
If we added an electric energy storage type regenerative braking system, we could recover 50% of energy from the total fuel economy loss.
While these technologies have not yet been integrated into production gasoline cars, they have the potential to significantly improve their mileage. However regenerative braking is a common feature of electric and hybrid cars, and is one of the reasons for those vehicles’ low fuel consumption.
1.7 Advantages of Regenerative Braking System
Increase of overall energy efficiency of a vehicle.
Improve Performance.
Emission Reduction.
Reduction in Engine Wear.
Cuts down on pollution related to electricity generation.
Increases the lifespan of friction braking systems.
Smaller Accessories.
Less use of traditional mechanical brakes leads to less wear over time
Chapter 2 Literature Review
The following papers from different science journals has been selected and referred for the aforesaid purpose. Along with the papers the books by different authors has also been referred. The list for the same is as given below.
What is Regenerative Braking Technology?
Figure 6: Regenerative Braking System (RBS)
The Figure 9 shows the basic layout of Regenerative Braking System. RBS is an important and useful system to reduce loss of energy during braking and shortage of the fuel resources problem. According to the conservation low of energy, energy can?t be created or destroyed but it can be converted from one form to another. RBS is a system which can convert mechanical energy to electrical energy. This system is used to recuperate the kinetic energy wasted during braking and converting it to a useful energy for conventional brake vehicle. When the conventional brake is applied energy is wasted.
The recuperate energy is then saved in a power storage for future usage. In Regenerative Braking System, the DC motor is used as a generator to recapture kinetic energy from the wheel of the vehicle into electrical energy. The conventional brake will continue to be used as an emergency brake. Because the RBS is only able to stop the vehicle in a relatively long distance and time. This situation would cause accident to occur.
How Regenerative Braking Works.
Regenerative braking is by no means a simple process. For a hybrid vehicle, the basic theory is as such: the internal combustion engine produces chemical energy from the fuel, a generator then acts to use this chemical energy to produce electrical energy that the electric traction motor drive will use to provide a torque to the wheels, propelling the vehicle forward. When the vehicle brakes, the opposite occurs and the wheels provide a negative torque to the electric traction motor, which causes the motor to run in reverse enabling it to act as a generator and produce energy that is then utilized to charge the car?s battery.
Table 1: Power Output of Engine with and Without Regenerative Braking
Hybrid Electric Vehicle Regenerative Braking Energy Recovery System
There are certain problems that arise when considering this basic theory that must be taken into consideration. For example, what can be done to prevent wasting of this recovered energy when the car?s batteries are fully charged? This recovered energy cannot be continuously pumped into a fully charged battery due to a high possibility of overheating. Therefore, the regenerative braking system must either be disconnected when the battery is fully charged, or preferably, the recovered energy has to be stored in a manner that would allow it to be later accessed to charge the battery once the charge on the battery began to deplete. U.S. patent no. 5,291,960 by Larry Brandenburg and Edward King introduces the first regenerative braking system that utilizes the energy generated during braking to recharge the main storage battery and also store the excess energy.
They also described other innovative ways to use this captured energy, for example, to preheat the internal combustion engine to reduce the extra carbon emissions produced from driving with a cold engine. Still, the most important aspect of a regenerative braking system is the component that generates the electrical energy that will be utilized to perform these functions. This component is the electric traction motor drive.
Comprehensive Efficiency Modeling of Electric Traction Motor Drives for Hybrid Electric Vehicle Propulsion Applications
The electric traction motor drive is the integral component in determining the efficiency of a regenerative braking system, as it is the part of the system that actually recovers the energy from braking. But, as the electric motor of the vehicle, it also provides the power in the form of electrical energy to the vehicle?s wheels, generating torque, and allowing the vehicle to propel forward.
When considering the electric traction motor drive in a hybrid or electric vehicle, many considerations must be taken into account to maximize the motor?s efficiency. In the propulsion of hybrid and electric vehicles, it is expected that the traction motor be utilized throughout the entire range of velocities and torques that the vehicle can achieve. Thus, the motor must be able to handle relatively frequent starting and stopping and rapid acceleration rates, which requires the motor to be able to produce a large amount of torque at all speeds.
High torque density, or the ratio of the torque produced by the motor to the mass of the motor system, is greatly desired. A lightweight electric traction motor with a high torque output will certainly help maximize a motor?s efficiency. Other attributes such as controllability and stability are required for a successful electric traction motor, and thus, the motor must be tested at all possible combinations of torques and velocities that the motor is capable of.
Analysis of a regenerative braking system for hybrid electric vehicles using an electro-mechanical brake
Figure shows the structure of the HEV investigated in this paper. The power source of this HEV is a 1.4 liter internal combustion engine and a 24 kW electric motor connected to one of the axes. The transmission and braking system are an Automated Manual Transmission (AMT) and an EMB system with pedal stroke simulator, respectively. EMB supplies braking torque to all four wheels independently, and the pedal stroke simulator mimics the feeling of the brake pedal on the driver?s foot.
Figure 7: Structure of the HEV
Figure shows the structure of the HEV investigated in this paper. The power source of this HEV is a 1.4 liter internal combustion engine and a 24 kW electric motor connected to one of the axes. The transmission and braking system are an Automated Manual Transmission (AMT) and an EMB system with pedal stroke simulator, respectively. EMB supplies braking torque to all four wheels independently, and the pedal stroke simulator mimics the feeling of the brake pedal on the driver?s foot.
Figure Configuration of HEV braking control system the vehicle controller determines the regenerative braking torque and the EMB torque according to various driving conditions such as driver input, vehicle velocity, Battery State of Charge (SOC), and motor characteristics. The Motor Control Unit (MCU) controls the regenerative braking torque through command signals from the vehicle controller. The Brake Control Unit (BCU) receives input from the driver via an electronic pedal and stroke simulator, and then transmits the braking command signals to each EMB. This is determined by the regenerative braking control algorithm from the value of remaining braking torque minus the regenerative braking torque. The braking friction torque is generated when the EMB in each wheel creates a suitable braking torque for the motor; the torque is then transmitted through the gear mechanism to the caliper.
An Intelligent Regenerative Braking Strategy for Electric Vehicles
The energy-saving, power-train efficiency and braking stability performance of electric vehicles depends to a large extent on their regenerative braking strategy. The article has analyzed the braking effectiveness and braking stability, and presented a fuzzy RBS to improve the braking performance. The fuzzy RBS effectively solves the braking force distribution between front and rear wheels, and the distribution between friction braking force and regenerative braking force. What?s more, the fuzzy RBS is applied and tested on a LF620 prototype EV on the road. Experimental results show that it can realize maximum recovery vehicle braking energy while meeting braking safety requirements. The power-train and component efficiency are evidently improved and the maximum driving range per charge of the EV can be extended. They are the most convincing evidence to verify the effectiveness of the regenerative braking method in recycling braking energy which otherwise is wasted as heat through friction.
Chapter 3 Abstract of entire review
Regenerative Braking is a process of reducing braking loss ; provide comfortable drive during braking and many more.
Researchers are interested for find out such system which can be utilized in conventional car also.
Research has already done on electric car and hybrid car by design change of such system ; different method used for recapture energy storage.
But it is also possible to use such system in conventional car by design change and finding analytical calculation for use of RBS in such car.
Chapter 4 Design Requirements of RBS
4.1 Objective of work
The main objective of regenerative breaking system is to recover as much as possible torque while brakes are being applied.
This technology of regenerative braking controls the speed of the vehicle by converting a portion of the vehicle?s kinetic energy into another useful form of energy.
The energy so produced could then be stored as electrical energy in the automobile battery, or as mechanical energy in flywheels, which can be used again by the vehicle.
4.2 Design Requirements
There are many requirements that need to be met to produce a product that is both feasible and optimal. There are also some constraints, both geometric and engineering that also need to be satisfied. The following list describes these requirements and constraints:
1. Store energy while braking
This is the main requirement and the overall objective of the device and must be suitable to meet the customer?s needs.
2. Return energy to start up
Once the energy is stored in the device, it is necessary to have a simple way to release this energy back to the user in a positive way. This can be accomplished with an innovative system.
3. Must fit on a car
This is one of the most difficult constraints to achieve and most important because we are dealing with such confined spacing.
4. Good stopping range
The stopping range is important because this product needs to be usable in real life situations. This component can be optimized to have the shortest stopping distance using dynamic analysis.
5. Good stopping force
The force required to stop is dependent on the stopping range and the comfort levels of the rider. It is also related to the possible dynamo/alternator features.
6. Inexpensive and affordable
This product must be able to make a profit and be desirable. The driving force for the price can be directly related to the dynamo/alternator?s size and supporting accessory.
7. Safe to user and environment friendly
Safety is always a very important aspect whenever there is a consumer product. This requirement will be addressed after the initial design is created.
8. Profitable
Profit is usually the main motivation for the start of any company; therefore this is one of the parameters that will be optimized.
9. Reliable
It is important to have a product that is reliable and this requirement will affect the long term business image and needs to be maintained in high regards.
10. Manufacturability
In order to make anything profitable, it needs to be manufacturability, hence the important of having a product that can be made easily and cheaply.
11. Aesthetically pleasing
This is not a requirement that needs to be taken heavily, but the design should always have nice look about it, because looks will persuade the buyer.
12. Modular
Having a device that can be adapted to existing car is essential to sell the greatest number of units. This also can reduce other types of manufacturing costs.
13. Should not hinder normal riding
To have a successful accessory for a car, the ride should not feel a noticeable change in the driving performance or in the normal driving motion. A device that impedes the normal riding experience would be considered undesirable.
14. Controlled release
The energy that is released back to the user must be done in a safe and manageable fashion. This can be a consideration after the prototype is completed.
4.3 Components of Model
There are following components which will be used in RBS mode
Quantity
Parts
1
A.C Motor
1
Alternator
2
Clutch
1
Tire
2
Pulley
2
Gear
6
Bearing
1
Battery
4.4 Arrangement of Components
Figure 8 Basic Construction of RBS Model
Figure shows the arrangement of RBS Model. In the figure Motor is connected with the driving pulley through shaft and clutch. Shaft is made of cast iron. Driving pulley is connected with driven pulley by using belt.
Driven pulley drives the shaft. One end of shaft is connected with flywheel and other end of shaft is connected with Alternator by using clutch and gears. Output power of Alternator is stored in battery after controlling by Power control unit.
4.5 How Model Will Work?
When the brake is not applied
When brake is not applied, and Clutch of driving shaft is connected at that time power is transmitted from motor to driving pulley. Driving pulley transmit power to driven pulley by using belt. Driven pulley drives the flywheel at that time the clutch which is connected to Alternator is disengaged so Alternator is not run. The power which is transmitted by A.C motor is stored in flywheel by means of kinetic energy
When the brake is applied
When the brake is applied clutch of driving shaft is disconnect pulley and ac motor. So power transmitted from ac motor to flywheel is cut off and the clutch which is connected to Alternator is engaged so the circuit from flywheel to Alternator is completed. In this case Kinetic energy which is stored in flywheel is transmitted to the Alternator from gears. From this kinetic energy Alternator rotates and produces power which will be stored in battery.
4.6 Motor Specification
Power 1 HP
RPM 920
Current rating 1.9 A
Voltage rating 240 V
Table 3: Motor Specification
Figure 9: AC Motor
Chapter 5 Analytical Methodology
Generally Regenerative Braking System used in Hybrid vehicles and Electric vehicles. In conventional cars friction brakes and other braking system are used but regenerative brakes do not used so we wastes lot of kinetic energy.
5.1 Analytical Calculation
We analytically calculate the loss of kinetic energy due to braking in the conventional car.
For calculation of the kinetic loss we consider the one car model “Maruti Alto 800”.
Following is the analytical calculation of conventional car “Maruti Alto 800”.
Specification of Alto 80013 Curb
Weight: 695 Kg
Gross Weight: 1185 Kg
Fuel Tank: 35 Liters Frontal
Area: 2.15 m2
Tyre Diameter: 12 inch
Max. Torque: 69 Nm @ 3500 rpm
Max. Power: 48 PS @ 6000 rpm
Fuel Economy: 22.74
City Mileage: 13.3
Highway Mileage: 17.8
Overall Mileage: 15.55
Final Drive Ratio: 4.35
Gear Ratio:
First Gear: 3.583
Second Gear: 2.166
Third Gear: 1.333
Forth Gear: 0.900
Reverse Gear: 3.363
Calculating kinetic energy loss by taking three different speeds of vehicle
V1=25 m/s
V2=40 m/s
V3=60 m/s
Resistance to the motion of the vehicle
1) Air Resistance
Air offers resistance to the movement of a vehicle. Air resistance is expressed as
= kaAv12
=0.02688×2.15×252
=36.12
= kaAv22 =0.02688×2.15×402
=92.46
= kaAv32
=0.02688×2.15×602
=208.05
2) Rolling resistance
It is the resistance experienced between tyre and road, and the friction in transmission system in wheel bearings. It is expressed as, Rr= (a+bv)W a=0.0112 b=0.00006
W=1185 kg
Rr1= (0.0112+0.00006×25)1185
= 15.0495
Rr2= (0.0112+0.00006×40)1185
= 16.116
Rr3= (0.0112+0.00006×60)1185
17.538
Torque of Driving Wheel At Different Gearing Position Tw = (g.r× a.r)×?t×TeTe
=69N.m @3500 rpm
Tw1= (3.583× 4.35)×0.92×69
= 989.40 Nm
Tw2= (2.166× 4.35)×0.92×69
= 598.11 Nm
Tw3= (1.333× 4.35)×0.92×69
= 368.091 Nm
Tw4= (0.900× 4.35)×0.92×69
248.52 Nm
Force Due To Rolling Resistance
Force due to rolling Resistance = co. efficient of rolling resistance× mass of vehicle × g
0.015 × 1185 × 9.81
174.19 N
Table 4: Rolling Friction Coefficient of Different Tire14
5) Work Done
Over the course of driving one kilometer, this will require extra energy given by: W = FRR × distance
=174.19 × 1000m =174190 Nm
= 174.19 kJ for each kilometer driven.
We can figure out how much fuel is required to drive one kilometer by using the efficiency formula:
Efficiency =
Efficiency
Fuel energy input =
= 766 kJ
And to provide this amount of energy we need to use
Energy per liters =
# of liters =
0.0239L
0.0239L fuel is required to drive 1 km
6)Kinetic Energy of Moving Object
Now we need to know how much energy it takes to get this mass moving again at difference velocity of vehicle. The kinetic energy of a moving object is given by KE = ½mv2, so the total kinetic energy required is
K.E
= 0.028 106 J
K.E
= 0.073148 106 J
K.E= 0.16458 106 J
City Mileage = 13.3 km/L
0.07518 L/km
Empty Mass = 695 kg
Let?s see how much work is done against air resistance for each kilometer a typical car driving at following different speed.
Work done against air resist =
W
1.3 kg/m3 2.15 0.30 1000 (6.944)2
20.215 kJ
W
1.3 kg/m3 2.15 0.30 1000 (11.11)2
51.75 kJ
W
1.3 kg/m3 2.15 0.30 1000 (16.66)2
= 116.46 kJ
We can figure out how much fuel is required for each kilometer travelled using the efficiency formula:
Efficiency
Fuel energy input
FI= 88.89 kJ
FI
= 227.57 kJ
FI
= 512.137 kJ
And to provide this amount of energy we need to use
Energy per liters
# of liters
For velocity,
# of liters
0.003L
# of liters
0.0071L
# of liters
= 0.016L
So, 0.003L, 0.0071L, 0.016L to overcome air drag of the each kilometers that car travels
7) Fuel Consumption due to Acceleration
Subtracting the above figures from the total fuel consumption for the Alto car allows us to figure out the fuel consumption just for the repeated acceleration due to stop-and-go driving. This gives
Consumption = Total fuel – fuel due to rolling – fuel due to air drag
For velocity,
Consumption = 0.0752 – 0.023 – 0.003
0.0492 L/km
Consumption = 0.0752 – 0.023 – 0.0071
0.0451 L/km
Consumption = 0.0752 – 0.023 – 0.016
= 0.0362 L/km
This tells us that repeated acceleration is responsible for about following percentage of the Alto’s city fuel economy
For velocity,
= 65%
= 59.9%
= 48.2%
From the above calculation we can say that, if we added regenerative braking system, we could recover above specified percentage of this energy, thereby saving (50%) (65%) = 32.5% at speed 25 m/s of the total city fuel economy! which suggests there may be some other complexities we haven’t considered. However, we are reasonably close to this number and these savings are definitely something to get excited about. While these technologies have not yet been integrated into production gasoline cars, they have the potential to significantly improve their mileage. However regenerative braking is a common feature of electric and hybrid cars, and is one of the reasons for those vehicles’ low fuel consumption.
5.2 Design of components
We will use the 1 HP motor in the model for driving the wheel.
For transmitting the torque and power following design and specification will use.
Torque calculation:
Power (P) =745.69 W
Speed (N) = 920 rpm
Torque (T) = (P×60) † (2×?×N)
= (745.69×60) † (2×?×920)
T = 7.74 Nm
= Say 8 Nm
Design of Shaft:
We use MS material for driving and driven shaft. So from the standard value of various physical property of this material listed below.
Ultimate shear stress ?u= 340 N/mm2
Ultimate bending stress ?u = 160 N/mm2
Young modules E =206*103 N/mm2
Factor of safety = 8
Diameter of shaft = d
Torsional shear stress (?) = ?u / F.S.
340/8
42.5 N/mm2
say 42 N/mm2
Torque (T) = 3
d3 = 970.57
d = 9.82 mm
= say 10 mm
From the standard design we take 18mm shaft diameter.
DESIGN OF PULLEY
Figure 10 Sectional View of pulley
Here we are using disc aluminum pulleys which have a disc for connecting rim to the shaft instant of arms as a hub in magnetic disc coupling. This is shown in figure below,
Figure 11 Flat Belt Pulley
Magnets are arranged inside of this pulley, so the various calculations for the design of the pulley are as follows:
From the standard dimension
Outer diameter of pulley (Do) = 6 ×d
= 6 ×18
= 108 mm
= say 110 mm
Width of flange of pulley (B) = 3 ×d
= 3 ×18
= 54 mm
Hub diameter (Dh) = 2 ×d
= 2 ×18
= 36 mm
Length of hub ( lh) = ×d×18
= 28.26
= say 30 mm
Length of hub should not be less then = ×B
= 36 mm
So we take maximum value from the above two value lh = 36 mm
Thickness of rim (t) = + 2 mm
+ 2 mm
=2.36 mm
say 3 mm
Thickness of disc = thickness of rim (t)
=3 mm
Check for shear failure
T = (? × D × t) × ? ×
8000 = (? × 110 × 3) × ? ×
? = 0.14 N/mm2
This value is less than design value design is safe.
REFERENCE
Research paper:
1 S. Williamson, A. Emadi, K. Ragashekara. “Comprehensive Efficiency Modeling of
Electric Traction Motor Drives for Hybrid Electric Vehicle Propulsion Applications.” Institute of
Electrical and Electronics Engineers, Published in: Vehicular Technology,
IEEE Transactions on Volume: 56, Issue Date: July 2007, ISSN: 0018-9545 Online Available:
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4273755&tag=1
Ahn, J., Jung, K., Kim, D., Jin, H., Kim, H. and Hwang, S. (2009). Analysis of a regenerative braking system for hybrid electric vehicles using an electro-mechanical brake, International Journal of Automotive Technology, Vol. 10(No. 2), pp. 229?234.
GuoqingXu, Weimin Li, Kun Xu, and Zhibin Song, An Intelligent Regenerative Braking Strategy for Electric Vehicles, ISSN 1996-1073, 2011, 4, 1461-1477; doi:10.3390/en4091461, pp. 1475 Patent:
L. R. Brandenburg, E. T. King. (1992, November 10). “Hybrid Electric Vehicle Regenerative Braking Energy Recovery System” United States Patent.
Marc Charles Gravino, Rockford, IL(US), (Jun. 18, 2013), REGENERATIVE
BRAKING SYSTEM, Patent No.: US 8,464,821 B2 Books:
Automobile Engineering Vol. 1 By Dr. Kripal Singh
Fundamentals of Machine Elements, 3rdeditionschmid, hamrock and jacobson
www.howstuffworks.com/brake.htm
Website: “What is Regenerative Braking Technology?” http://www.brighthub.com/environment/renewable-energy/articles/57860.aspx
10 C. Lampton. “How Regenerative Braking Works.” How Stuff Works. Online.
Available: http://auto.howstuffworks.com/auto-parts/brakes/brake-types/regenerative-braking5.htm
Nice, Karim (2000-08-22). “How Power Brakes Work” (http://www.howstuffworks.com/autoparts/ brakes/brake-types/power-brake.htm). Howstuffworks.com. Retrieved 2011-03-12.
www.brighthub.com
www.marutisuzuki.com/alto800.aspx
http://c21.phas.ubc.ca/article/energy-use-cars-3-rolling-resistance
http://www.eminebea.com/en/engineering_info/rotary/clutch_brake/clutch_brake/ cat-1/002.shtml
http://www.indiamart.com/microlinkenterprises/pulleys-bushes.html
