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A SEMINAR REPORT ON REGENERATIVE BRAKING SYSTEM
SUBMITTED BY:
GUIDED BY: -
ACKNOWLEDGEMENT This acknowledgement is a humble attempt to earnestly thank all those who were directly or indirectly involved in preparation of this seminar report. I n p a r t i c u l a r I a m t h a n k f u l t o m y g u i d e M r. K a l p e s h D . M a n i a who guide me in my seminar work. I am thankful to him for taking active part in the preparation of my seminar report. It was impossible to present this report without his co-operation and suggestion.
Last but not least I would like to express out deep sense of gratitude
to
all
the
faculty
of
Mechanical
Engineering
Department and also my friends who help me to accomplish what I have s t a r t e d f o r.
DEPARTMENT OF MECHANICAL ENGINEERING THE SEMINAR REPORT ON :
REGENERATIVE BRAKING SYSTEM PREPARED BY: GUIDED BY: EXAMINER
H.O.D
(1) ___________________ (2) ___________________ (3) ___________________ (4) ___________________
ABSTRACT Regenerative Braking System is the way of slowing vehicle by using the motors as brakes.
Instead of the surplus energy of the vehicle
being wasted as unwanted heat, the motors act as generators and return s o m e o f i t t o t h e o v e r h e a d w i r e s a s e l e c t r i c i t y. The vehicle is primarily powered from the electrical energy generated from the generator, which burns gasoline.
This energy is stored in a
l a r g e b a t t e r y, a n d u s e d b y a n e l e c t r i c m o t o r t h a t p r o v i d e s m o t i v e f o r c e to the wheels. The regenerative barking taking place on the vehicle is a way to obtain more efficiency; instead of converting kinetic energy to thermal energy through frictional braking, the vehicle can convert a g o o d f r a c t i o n o f i t s k i n e t i c e n e r g y b a c k i n t o c h a r g e i n t h e b a t t e r y, u s i n g t h e s a m e p r i n c i p l e a s a n a l t e r n a t o r.
LIST OF FIGURES Fig. 1
G r a p h i c a l r e p r e s e n t a t i o n o f e n e r g y u s a g e b e t w e e n t w o v e h i c l e s.
Fig. 2
Mercury Hybrid Mariner
Fig. 3
R e g e n e r a t i v e B r a k i n g S ys t e m U s i n g N i t i n o l S p r i n g .
CONTENTS
1. INTRODUCTION 2. NECESSITY OF THE SYSTEM 3. REGENRATIVE BRAKE 4. ELEMENTS OF THE SYSTEM 5. DESCRIPTION & OPERATION 6. RESULTS 7. CONCLUSION
CHAPTER 1: INTRODUCTION
Brake:A brake is a machine element and its principle object is to absorb energy during deceleration.
In vehicle brakes are used to absorb
kinetic energy whereas in hoists or elevators brakes are also used to absorb
potential
stationary frame, e n e r g y.
e n e r g y. normally
By
connecting
the
brake converts
moving
kinetic
member
energy to
to
heat
This causes wastage of energy and also wearing of frictional
lining material. Regenerative Braking System:Regenerative Braking System is the way of slowing vehicle by using the motors as brakes.
Instead of the surplus energy of the
vehicle being wasted as unwanted heat, the motors act as generators a n d r e t u r n s o m e o f i t t o t h e o v e r h e a d w i r e s a s e l e c t r i c i t y. The vehicle is primarily powered from the electrical energy generated from the generator, which burns gasoline.
This energy is stored in a
l a r g e b a t t e r y, a n d u s e d b y a n e l e c t r i c m o t o r t h a t p r o v i d e s m o t i v e f o r c e to the wheels. The regenerative barking taking place on the vehicle is a way to obtain more efficiency; instead of converting kinetic energy to
thermal energy through frictional braking, the vehicle can convert a g o o d f r a c t i o n o f i t s k i n e t i c e n e r g y b a c k i n t o c h a r g e i n t h e b a t t e r y, u s i n g t h e s a m e p r i n c i p l e a s a n a l t e r n a t o r. T h e r e f o r e , i f yo u d r i v e l o n g d i s t a n c e w i t h o u t b r a k i n g , yo u ’ l l b e powering the vehicle entirely from gasoline. The regenerative braking Regenerative Braking System comes into its own when you’re driving i n t h e c i t y, a n d s p e n d i n g a g o o d d e a l o f yo u r t i m e b r a k i n g . You w i l l s t i l l u s e m o r e f u e l i n t h e c i t y f o r e a c h m i l e yo u d r i v e t h a n o n t h e h i g h w a y, t h o u g h . ( T h e r m o d y n a m i c s t e l l s u s t h a t a l l i n e f f i c i e n c y c o m e s f r o m h e a t g e n e r a t i o n . F o r i n s t a n c e , w h e n yo u b r a k e , t h e b r a k e p e d a l s h e a t u p a n d a q u a n t i t y o f h e a t , o r e n e r g y, i s l o s t t o t h e o u t s i d e w o r l d . F r i c t i o n i n t h e e n g i n e p r o d u c e s h e a t i n t h e s a m e w a y. Heat
e n e r g y,
also,
has
higher
entropy
than,
s a y,
electric,
meaning that it is less ordered.) Definition: Braking method in which the mechanical energy from the load is converted into electric energy and regenerated back into the line is known as Regenerative Braking.
The Motor operates as
g e n e r a t o r. R e g e n e r a t i v e B r a k i n g F o r H y b r i d Veh i c l e : I n m o s t e l e c t r i c a n d h y b r i d e l e c t r i c v e h i c l e s o n t h e r o a d t o d a y, t h i s i s a c c o m p l i s h e d b y o p e r a t i n g t h e t r a c t i o n m o t o r a s a g e n e r a t o r, providing braking torque to the wheels and recharging the traction batteries.
The energy provided by regenerative braking can then be
used for propulsion or to power vehicle accessories.
CHAPTER 2: NECESSITY OF THE SYSTEM The regenerative braking system delivers a number of significant advantages over a car that only has friction brakes. In low-speed, stopand-go traffic where little deceleration is required; the regenerative braking system can provide the majority of the total braking force. This vastly improves fuel economy with a vehicle, and further enhances the attractiveness of vehicles using regenerative braking for city d r i v i n g . At h i g h e r s p e e d s , t o o , r e g e n e r a t i v e b r a k i n g h a s b e e n s h o w n t o contribute to improved fuel economy – by as much as 20%. Consider a heavy loaded truck having very few stops on the road. I t i s o p e r a t e d n e a r m a x i m u m e n g i n e e f f i c i e n c y. T h e 8 0 % o f t h e e n e r g y produced is utilized to overcome the rolling and aerodynamic road forces.
The energy wasted in applying brake is about 2%.
Al s o i t s
brake specific fuel consumption is 5%. Now consider a vehicle, which is operated in the main city where t r a f f i c i s a m a j o r p r o b l e m h e r e o n e h a s t o a p p l y b r a k e f r e q u e n t l y. F o r such vehicles the wastage of energy by application of brake is about 60% to 65%.
An d a l s o i t i s i n e f f i c i e n t a s i t s b r a k e s p e c i f i c f u e l
consumption is high.
Road 80%
Rake 65% Other 18%
Brake 2%
HEAVY LOADED TRUCK
Road 26% other 9%
CITY BUS
2.1 Graphical representation of energy usage between two vehicles.
S o me
of
the
a d v an t a g e s
of
reg e n e r a t i v e
b r a ki n g
over
c o n v e n t i o n a l b r a ki n g a re a s f o l l ow s : Energy Conservation: T h e f l yw h e e l a b s o r b s e n e r g y w h e n b r a k i n g v i a a c l u t c h s ys t e m s l o w i n g t h e c a r d o w n a n d s p e e d i n g u p t h e w h e e l . To a c c e l e r a t e , a n o t h e r c l u t c h s ys t e m c o n n e c t s t h e f l yw h e e l t o t h e d r i v e t r a i n , s p e e d i n g u p t h e c a r a n d s l o w i n g d o w n t h e f l yw h e e l .
Energy is therefore conserved rather than
wasted as heat and light which is what normally happens in the c o n t e m p o r a r y s h o e / d i s c s ys t e m . Wea r R e d u c t i o n : An electric drive train also allows for regenerative breaking which increases Efficiency and reduces wear on the vehicle brakes.
In
regenerative raking, when the motor is not receiving power from the battery pack, it resists the turning of the wheels, capturing some of the energy of motion as if it were a generator and returning that energy to the battery pack.
In mechanical brakes; lessening wear and extending
brake life is not possible. This reduces the use of use the brake. Fuel Consumption: The fuel consumption of the conventional vehicles and regenerative b r a k i n g s ys t e m v e h i c l e s w a s e v a l u a t e d o v e r a c o u r s e o f v a r i o u s f i x e d urban driving schedules. The results are compared as shown in figure. R e p r e s e n t i n g t h e s i g n i f i c a n t c o s t s a y i n g t o i t s o w n e r, i t h a s b e e n proved the regenerative braking is very fuel-efficient. Braking is not total loss: C o n v e n t i o n a l b r a k e s a p p l y f r i c t i o n t o c o n v e r t a v e h i c l e ’s k i n e t i c e n e r g y into heat. In energy , therefore, braking is a total loss: once heat is generated, it is very difficult to reuse.
The regenerative braking
s ys t e m , h o w e v e r, s l o w s a v e h i c l e d o w n i n a d i f f e r e n t w a y.
CHAPTER 3 :REGENERATIVE BRAKING SYSTEM . A regenerative brake is an apparatus, a device or system which allows a vehicle to recapture and store part of the kinetic energy that would otherwise be 'lost' to heat when braking.
The IMA operating principle
Honda's patented IMA concept is quite simple - use an efficient Otto engine supplemented by an electric motor when additional power is n e e d e d . Al s o r e f e r r e d t o a s a ' h yb r i d ' s ys t e m b e c a u s e i t u s e s t w o p o w e r s o u r c e s , t h e I M A c o n c e p t a l l o w s t h e C i v i c H yb r i d t o u s e a s m a l l e r gasoline engine without any significant loss in performance.
T h i s s ys t e m i s e s p e c i a l l y e f f e c t i v e d u e t o t h e f a c t t h a t a c c e l e r a t i o n requires a significantly higher power than needed for cruising on a level r o a d ( w h e r e v e h i c l e s s p e n d m o s t o f t h e i r t i m e ) . An e n g i n e m o r e powerful than needed has to work under low load most of the time, condition where its efficiency is lower than under high loads, thus w o r s e n i n g t h e v e h i c l e ' s f u e l e c o n o m y..
The electric motor-generator positioned between the engine and transmission assists the engine when accelerating and recovers energy to store in batteries when braking or decelerating (regenerative braking), allowing it to operate independently without the need for a grid power s u p p l y. W h e n t h e C i v i c H yb r i d i s c o a s t i n g o r i t s b r a k e s a r e a p p l i e d , i t s e l e c t r i c m o t o r b e c o m e s a g e n e r a t o r, c o n v e r t i n g f o r w a r d m o m e n t u m ( k i n e t i c e n e r g y) i n t o e l e c t r i c a l e n e r g y, i n s t e a d o f w a s t i n g i t a s h e a t d u r i n g conventional braking. Energy is stored in a battery pack located behind t h e r e a r s e a t i n t h e t r u n k . I f t h e s t a t e o f c h a r g e o f t h e b a t t e r i e s i s l o w, the motor-generator will also recharge them while the Civic Hybrid is cruising.
CHAPTER 4: ELEMENTS OF THE SYSTEM There are three basic element required which are necessary for the working of regenerative braking system, these are : 1.Energy Storage Unit (ESU): The ESU performs two primary functions 1.TO recover & store braking energy 2. TO absorb excess engine energy during light load operation The selection criteria for an effective energy storage includes 1. High specific energy storage density 2. High energy transfer rate 3. Small space requirement The energy recaptured by regenerative braking might be stored in one of
three
devices:
an
electrochemical
b a t t e r y,
a
f l yw h e e l ,
in
a
regenerative fuel cell. Regen and Batteries: Wi t h t h i s s ys t e m , t h e e l e c t r i c m o t o r o f a c a r b e c o m e s a g e n e r a t o r w h e n the brake pedal is applied. The kinetic energy of the car is used to g e n e r a t e e l e c t r i c i t y t h a t i s t h e n u s e d t o r e c h a r g e t h e b a t t e r i e s . Wit h t h i s s ys t e m , t r a d i t i o n a l f r i c t i o n b r a k e s m u s t a l s o b e u s e d t o e n s u r e t h a t t h e c a r s l o w s d o w n a s m u c h a s n e c e s s a r y. T h u s , n o t a l l o f t h e k i n e t i c energy of the car can be harnessed for the batteries because some of it is "lost" to waste heat. Some energy is also lost to resistance as the energy travels from the wheel and axle, through the drivetrain and e l e c t r i c m o t o r, a n d i n t o t h e b a t t e r y. F o r e x a m p l e , t h e Toyo t a P r i u s c a n o n l y r e c a p t u r e a b o u t 3 0 % o f t h e v e h i c l e s k i n e t i c e n e r g y. The Honda Insight is another vehicle in addition to the Prius that is on the market and currently uses regenerative braking. In the Insight there are two deceleration modes: When the throttle is engaged, but the brake
p e d a l i s n o t , t h e v e h i c l e s l o w s d o w n g r a d u a l l y, a n d t h e b a t t e r y r e c e i v e s a partial charge.
When the brake pedal is depressed, the battery receives a higher c h a r g e , w h i c h s l o w s t h e v e h i c l e d o w n f a s t e r. T h e f u r t h e r t h e brake pedal is depressed, the more the conventional friction brakes are employed.
I n t h e I n s i g h t , t h e m o t o r / g e n e r a t o r p r o d u c e s AC , w h i c h i s c o n v e r t e d into DC, which is then used to charge the Battery Module. The Insight, a s w e l l a s a l l o t h e r r e g e n e r a t i v e s ys t e m s , m u s t h a v e a n e l e c t r i c controller that regulates how much charge the battery receives and how much the friction brakes are used. Regen and Flywheels: I n t h i s s ys t e m , t h e t r a n s l a t i o n a l e n e r g y o f t h e v e h i c l e i s t r a n s f e r r e d i n t o r o t a t i o n a l e n e r g y i n t h e f l yw h e e l , w h i c h s t o r e s t h e e n e r g y u n t i l i t i s n e e d e d t o a c c e l e r a t e t h e v e h i c l e . T h e b e n e f i t o f u s i n g f l yw h e e l technology is that more of the forward inertial energy of the car can be captured than in batteries, because the flywheel can be engaged even during relatively short intervals of braking and acceleration. In the case of batteries, they are not able to accept charge at these rapid i n t e r v a l s , a n d t h u s m o r e e n e r g y i s l o s t t o f r i c t i o n . An o t h e r a d v a n t a g e of flywheel technology is that the additional power supplied by the f l yw h e e l
during
acceleration
substantially
supplements
the
o u t p u t o f t h e s m a l l e n g i n e t h a t h yb r i d v e h i c l e s a r e e q u i p p e d w i t h .
power
2 . C o n t i n u o u s l y Var i a b l e Tra n s m i s s i o n ( C V T ) : The energy storage unit requires a transmission that can handle torque and speed demands in a steeples manner and smoothly control energy flow to and from the vehicle wheels. continuously
variable
transmission
and
F o r t h e f l yw h e e l t h e
vehicle
because
flywheel
rotational speed increases when vehicle speed decreases and vice versa. F l yw h e e l c a n w o r k w e l l w i t h e i t h e r m e c h a n i c a l o r h yd r o s t a t i c continuously variable transmission. 3. Control System : An “ON-OFF” engine control system is used. That means that the engine is “ON” until the energy storage unit has been reached the desired charge capacity and then is decoupled and stopped until the energy storage unit charge fall below its minimum requirement.
C H A P T E R 5 : DESCRIPTION & OPERATION How regenerative braking system works? R e g e n e r a t i v e ( o r D yn a m i c B r a k i n g ) o c c u r s w h e n t h e v e h i c l e i s i n motion, such as coasting, traveling downhill or braking. accelerator pedal is not being depressed.
An d t h e
During “Regent,” the motor
becomes a generator and sends energy back to the batteries. It is explained as follows, because the wheels of a decelerating vehicle are still moving forward, they can be made to turn the electric m o t o r, w h i c h t h e n f e e d s e n e r g y t o t h e b a t t e r i e s f o r s t o r a g e . T h e s ys t e m b e c o m e s , i n e f f e c t , a g e n e r a t o r, w h i c h p r o v i d e s b r a k i n g f o r c e w h i l e i t c o n v e r t s t h e v e h i c l e ’s k i n e t i c e n e r g y i n t o a r e u s a b l e f o r m - e l e c t r i c a l e n e r g y. When the accelerator pedal is released, the absence of pressure triggers a response from the Energy Storage Unit (ESU).
Regenerative
braking begins, and the batteries are re-charged by the motor, which is turned by the wheels. In this case, the friction brakes are not engaged. If more vigorous deceleration is required, and the brake pedal is depressed, this engages both sets of brakes.
H o w e v e r, t o m a x i m i z e
e n e r g y e f f i c i e n c y, i t i s a d v a n t a g e o u s t o a p p l y t h e r e g e n e r a t i v e b r a k e a s such as possible – it therefore tends to do more of its total work in the first part of the braking motion. There are two deceleration modes: 1. Foot off throttle but not on brake pedal – in this mode, the charge/assist gauge will show partial charge, and the vehicle will slow d o w n g r a d u a l l y.
2. Foot on brake pedal - In this mode, a higher amount of regeneration w i l l b e a l l o w e d , a n d t h e v e h i c l e w i l l s l o w m o r e r a p i d l y.
During light
brake pedal application, only the IMA motor//generator is slowing the c a r.
Wit h h e a v i e r b r a k e p e d a l a p p l i c a t i o n , t h e c o n v e n t i o n a l f r i c t i o n
b r a k e s a l s o c o m e i n t o p l a y. W h e n d e c e l e r a t i n g , r e g e n e r a t i o n w i l l c o n t i n u e u 8 n t i l e n g i n e s p e e d f a l l s t o a b o u t 1 0 0 0 r p m . At t h i s p o i n t , t h e driver will typically shift into neutral.
EXAMPLE
Mercury Hybrid Mariner 1. Mercury Mariner Hybrid P r o d u c t i o n P u l l a h e a d : P r o d u c t i o n b e g i n s a ye a r ahead of schedule Growing the Mercury Brand: New models and goals Distinctive Design: Mariner features clean lines, careful craftsmanship P o w e r P l a y : F u l l - h yb r i d g a s o l i n e a n d e l e c t r i c p o w e r t r a i n D yn a m i c C h a s s i s : N i m b l e h a n d l i n g a n d a s m o o t h , q u i e t r i d e Distinguished Safety: Full array of safety features Green Mission: Ford Motor Company's strategy for sustainability in vehicles T h e M e r c u r y M a r i n e r H yb r i d o f f e r s a u n i q u e l y s a t i s f yi n g t r a n s p o r t a t i o n choice for an ever-increasing segment of the population concerned about the environment. It's a stylish, upscale sport-utility vehicle with nimble handling and impressive performance, as well as ample cargo a n d t o w i n g c a p a c i t y. I n a d d i t i o n , i t ' s a n e n v i r o n m e n t a l l y c o n s c i o u s SUV with remarkable fuel economy – an estimated 33 miles per gallon ( m p g ) c i t y, 2 9 m p g h i g h w a y – a n d i s e x p e c t e d t o m e e t t h e c l e a n e s t emissions rating achievable by a fossil-fuel vehicle (California's A d v a n c e d Tec h n o l o g y P a r t i a l Z e r o E m i s s i o n s Veh i c l e s t a n d a r d ) .
Engineers placed the additional hybrid powertrain components low and t o t h e r e a r, t o l o w e r t h e c e n t e r o f g r a v i t y a n d i m p r o v e t h e c o n v e n t i o n a l Mariner's front-rear weight distribution. The rack-and-pinion steering is electrically assisted, rather than using t h e t r a d i t i o n a l h yd r a u l i c s t e e r i n g p u m p f o r c o n s i s t e n t s t e e r i n g e f f o r t s and control whether the gasoline engine is stopped or running. Regenerative braking uses the traction motor to assist the four-wheel disc brakes in slowing Mariner Hybrid while simultaneously generating e l e c t r i c i t y f o r c h a r g i n g t h e b a t t e r y.
R e g e n e r a t i v e b r a k i n g o f Toy o t a P r i u s : Toyo t a r e a l i z e d t h a t o n e w a y t o a c h i e v e l o n g e r v e h i c l e r a n g e w a s
to conserve and reuse some of the energy that a vehicle normally loses as heat caused by braking friction. This idea led engineers to apply the principles of regenerative braking. I n a l l Toy o t a v e h i c l e s t h a t f e a t u r e t h e r e g e n e r a t i v e b r a k i n g s ys t e m , t h e r e g e n e r a t i v e b r a k e i s o n l y r e s p o n s i b l e f o r a p a r t o f t h e deceleration necessary to stop the vehicle.
I n a n E V, t h i s f r a c t i o n i s
d e t e r m i n e d b y t h e v e h i c l e ’s s p e e d w h e n b r a k i n g i s i n i t i a t e d .
The
r e m a i n i n g b r a k i n g f o r c e i s p r o v i d e d b y t h e v e h i c l e ’s f r i c t i o n b r a k e s . To m a x i m i z e f u e l e c o n o m y, o f c o u r s e , t h e r e g e n e r a t i v e b r a k i n g s ys t e m is made to do as much of the braking work as possible.
C o m p o n e n t U s e d i n Toy o t a P r i u s f o r R e g e n e r a t i v e B r a k i n g S y s t e m : Brake Pedal: I t i s u s e d t o a p p l y b r a k i n g f o r c e b y t h e d r i v e r. Hydraulic Booster Unit: I t i s c o m p o s e d o f t h e m a s t e r c y l i n d e r a n d t h e r e g u l a t o r, r e s p o n d s i n two steps. First it signals electronically to the brake ECU that braking force has been demanded. pressure
on
the
pedal
Next, the master cylinder exerts hydraulic
stroke
simulator,
and
the
regulator
feeds
h yd r a u l i c f l u i d t o t h e h yd r a u l i c p r e s s u r e c o n t r o l u n i t . Brake ECU: The brake ECU senses the braking demand and sends a fraction of this demand to the THSECU for regenerative braking. It also calculates the force necessary to fulfill remaining braking demand and instruct the hydraulic pressure control unit to on a corresponding amount of hydraulic fluid Pedal Stroke Simulator: I t a b s o r b s a n a m o u n t o f h yd r a u l i c p r e s s u r e f r o m m a s t e r c y l i n d e r t h a t corresponds to the amount of braking force applied by the regenerative braking system. A s h yd r a u l i c p r e s s u r e i s f e d b a c k t o t h e p e d a l , t h e p e d a l , t h e p e d a l s t r o k e s i m u l a t o r f e e d s b a c k t o t h e m a s t e r c yl i n d e r.
T H S ( Toy o t a H y b r i d S y s t e m ) E C U : It induces regenerative braking, and returns a signal that indicates braking force output back to the brake ECU. Hydraulic Pressure Control Unit: It es on a corresponding amount of hydraulic fluid to a four way c yl i n d e r.
C H A P T E R 6: R E S U LT Regenerative
braking
technology
is
one
more
positive
step
f o r w a r d i n Toyo t a ’s q u e s t t o r e a l i z e t h e u l t i m a t e e c o c a r. B y w o r k i n g i n concert with previously developed electric motor technologies, its application
helps
Toyo t a ’s
electric
vehicles
and
h yb r i d
vehicles
(including the recently released prius) to achieve extended ranges and t o b e f r i e n d l i e r t o t h e e n v i r o n m e n t t h a n e v e r b e f o r e . At t h e s a m e t i m e , this new technology remains unobtrusively in the background; drivers b e n e f i t f r o m r e g e n e r a t i v e b r a k i n g w h i l e e n j o yi n g t h e s a m e f i r m b r a k i n g feel found in conventionally equipped vehicles.
Wheel Rotating Device.
Wheel – A Rotating Device – B Shafts – C.D. Gearbox –E Clutch – G Spring - H
Shafts.
Gearbox
Clutch
Spring
7.1 Regenerative braking system using Nitinol Spring
A hydraulic regenerative braking system improves the fuel economy of Ford's F-350 Tonka 25-35% during stop-andgo driving. The system provides power during initial acceleration when demand peaks.
T h e H L A s y s t e m c o n s i s t s o f a r e v e r s i b l e h yd r a u l i c p u m p / m o t o r f r o m Eaton's Fluid Power Group (Eden Prairie, MN) coupled to the drive s h a f t t h r o u g h a c l u t c h a n d t w o a c c u m u l a t o r s . As t h e d r i v e r s t e p s o n t h e brake, the pump/motor forces hydraulic fluid out of a low-pressure a c c u m u l a t o r a n d i n t o a h i g h - p r e s s u r e a c c u m u l a t o r, i n c r e a s i n g t h e pressure of nitrogen gas stored there to 5,000 psi. D u r i n g a c c e l e r a t i o n , t h e H L A s ys t e m s w i t c h e s f r o m t h e p u m p m o d e t o t h e m o t o r m o d e , t h e n i t r o g e n g a s f o r c e s t h e h yd r a u l i c f l u i d b a c k i n t o t h e l o w - p r e s s u r e a c c u m u l a t o r, a n d t h e p u m p / m o t o r a p p l i e s t o r q u e t o t h e driveshaft through the clutch. If quick acceleration is required, the F3 5 0 ' s d i e s e l e n g i n e w o r k s w i t h t h e H L A s ys t e m
T h e h y d r a u l i c l a u n c h a s s i s t s y s t e m i n t h e F - 3 5 0 Ton k a f u n c t i o n s a s a secondary source of energy during peak power demand. It consists of a low-pressure accumulator in blue, and a high-pressure accumulator in r e d . T h e s y s t e m c a p t u r es e n e r g y n o r m a l l y d i s s i p a t e d a s h e a t d u r i n g b r e a k i n g , s t o r es i t , a n d u s e s i t l a t e r d u r i n g p e r i o d s o f p e a k p o w e r demand. Eighty percent of the initial kinetic energy is returned to the vehicle. " T h e s y s t e m s t o r e s a p p r o x i m a t e l y 3 8 0 k J o f e n e r g y," s a ys B r a d Bohlmann, a mechanical engineer and business development c o o r d i n a t o r i n Ad v a n c e d Tec h n o l o g y a t E a t o n ' s F l u i d P o w e r G r o u p . " Wi t h t h a t m u c h e n e r g y, w e c a n a c c e l e r a t e a 1 0 , 0 0 0 - l b v e h i c l e f r o m a dead stop to between 25 and 30 miles per hour with no assistance from the vehicle's combustion engine." "Ford thinks that both electric and hydraulic regenerative systems have a f u t u r e , " s a ys J o h n B r e v i c k , a F o r d m e c h a n i c a l e n g i n e e r w o r k i n g o n the HLA system. "But for heavy vehicles like our 10,000-lb F-350 trucks, hydraulics are better at capturing lost energy than electric s ys t e m s . " Eaton's Bohlmann explains that the real advantage of hydraulics is in i t s p o w e r d e n s i t y. " H y d r a u l i c s i s c a p a b l e o f t r a n s f e r r i n g e n e r g y v e r y q u i c k l y," s a ys B o h l m a n n . " T h e r a t e o f e n e r g y t r a n s f e r i s i n a h y b r i d e l e c t r i c s ys t e m o f a s i m i l a r s i z e i s m u c h l o w e r." Bohlmann adds that the specific vocation or driving cycle of the v e h i c l e d e t e r m i n e s w h e t h e r a h y b r i d h yd r a u l i c o r h yb r i d e l e c t r i c s y s t e m is best suited for the vehicle. "Think of hydraulics as a sprinter,
p r o v i d i n g f a s t b u r s t s o f p o w e r," h e s a ys . " A n e l e c t r i c h yb r i d i s m o r e l i k e a m a r a t h o n r u n n e r." " T h e c h a l l e n g e n o w i s t o m a k e u s e o f t h e r e g e n e r a t i v e b r a k i n g s ys t e m s e a m l e s s t o t h e c u s t o m e r ," s a y s F o r d ' s B r e v i c k . " We s t i l l h a v e r o o m f o r i m p r o v e m e n t s a n d f e e l t h e H L A s ys t e m h a s a l o t o f p o t e n t i a l . " As for the future, Ford, Eaton, and the U.S. Environmental Protection A g e n c y ( E PA) a r e j o i n t l y c o n d u c t i n g r e s e a r c h o n h y d r a u l i c h yb r i d vehicles, including internal combustion engines that would produce h yd r a u l i c p r e s s u r e t o d r i v e t h e v e h i c l e . E a t o n s i g n e d b o t h a t e c h n o l o g y license agreement and a cooperative research and development a g r e e m e n t w i t h t h e E PA f o r t h e d e v e l o p m e n t o f f u t u r e g e n e r a t i o n s ys t e m s . Inertia, Force and Mass E v e r yt h i n g h a s i n e r t i a ; i f i t h a s a m a s s , i t h a s i n e r t i a . A h y b r i d r e c l a i m s e n e r g y t h r o u g h t h e f u n d a m e n t a l s o f p h ys i c s . D o yo u r e m e m b e r any high school or college physics? You a p p l y a f o r c e t o m o v e a n o b j e c t . T h e e q u a t i o n f o r t h i s i s : F=ma “F” being the force, “m” being the mass and “a” being the acceleration The faster you want an object to accelerate, the more force you have to a p p l y. L e t ’s j u s t l o o k a t t h e e l e c t r i c m o t o r f o r n o w. E n e r g y f r o m t h e b a t t e r y ( Wat t s ) i s a p p l i e d t o t h e c o i l w i n d i n g s i n t h e m o t o r. T h e s e w i n d i n g s then produce a magnetic force on the rotor of the motor, which produces torque on the output shaft. This torque is then applied to the wheels of the car via a coupling of gears and shafts. When the wheel turns, it applies a force to the ground, which due to friction between the wheel and the ground causes the vehicle to move along the surface. T h i s i s l i k e i f yo u w e r e i n a b o a t a t a d o c k , a n d y o u g r a b b e d t h e d o c k a n d p u s h e d w i t h yo u r a r m . T h e f o r c e y o u a r e g e n e r a t i n g i s m o v i n g t h e b o a t r e l a t i v e t o t h e l o c a t i o n o f t h e d o c k . T h e m o r e f o r c e y o u a p p l y, t h e f a s t yo u g e t t h e b o a t t o m o v e . Friction in Hybrids T h e r e i s f r i c t i o n e v e r yw h e r e i n t h e h y b r i d s ys t e m . T h e r e i s e l e c t r i c a l friction between the atoms and electrons moving in the wires between the battery and the motor and through the motor itself. There is magnetic friction in the metal laminations that make up the magnetic
circuit of the motor, as well as in the magnets again on the atomic level. Then, there is mechanical friction between every moving part, s u c h a s t h e b e a r i n g s , s e a l s , g e a r s , c h a i n s a n d s o o n . T h e b y- p r o d u c t o f f r i c t i o n i s h e a t . Tak e y o u r h a n d s r u b t h e m t o g e t h e r a n d yo u r p a l m s g e t w a r m . T h e f a s t e r y o u d o i t , t h e f a s t e r t h e y h e a t u p . Al s o , t h e h a r d e r they are pressed together, the faster they will heat. Friction is energy lost to heat. When all of these losses are added up, that is what determines the efficiency of the vehicle. Frictional Losses in Conventional Cars A standard car generates torque to move the wheels to drive the vehicle down the road. During this time, it is generating friction and losses. W h e n yo u a p p l y s t a n d a r d b r a k e s , i t i s j u s t a n o t h e r f r i c t i o n d e v i c e t h a t has specially designed material to handle the heat from friction, which is applied to the drums and rotors that stop the wheel from turning. The friction between the wheel and the ground stops the vehicle. This standard vehicle has frictional losses to move the vehicle—and uses the f u n d a m e n t a l b e h i n d f r i c t i o n a l l o s s e s t o s t o p t h e v e h i c l e . S o i t ’s a l o s e lose situation. Tra n s f e r r i n g Tor q u e B a c k t o t h e M o t o r This inertia is the fundamental property of physics that is used to reclaim energy from the vehicle. Instead of using 100% of the foundation brakes of the vehicle, which are the friction brakes, we now let the linkages back to the motor such as the drive shafts, chains, and gears transfer the torque from the wheels back into the motor shaft. One of the unique things about most electric motors is that electrical energy can be transferred into mechanical energy and also mechanical e n e r g y c a n b e t r a n s f e r r e d b a c k i n t o e l e c t r i c a l e n e r g y. I n b o t h c a s e s , t h i s c a n b e d o n e v e r y e f f i c i e n t l y. T h u s , t h r o u g h t h e t e c h n o l o g y o f t h e m o t o r a n d m o t o r c o n t r o l l e r, t h e force at the wheels becomes torque on the electric motor shaft. The magnets on the shaft of the motor (called the rotor—the moving part of the motor) move past the electric coils on the stator (the stationary part of the motor) ing the magnetic fields of the magnets through the c o i l s p r o d u c i n g e l e c t r i c i t y. T h i s e l e c t r i c i t y b e c o m e s e l e c t r i c a l e n e r g y, w h i c h i s p u m p e d b a c k t o t h e b a t t e r y. T h i s , i n t u r n , c h a r g e s t h e h yb r i d battery pack. This is where the comment “regeneration” or “reclaiming e n e r g y” c o m e s f r o m . T h a t i s t h e b a s i c s o f h o w r e g e n e r a t i o n w o r k s . H o w m u c h e n e r g y yo u can reclaim depends on a lot of factors. There are different regeneration theories and designs, which fall into two groups: one being called parallel regen and the other called series regen, which are d i f f e r e n t f r o m t h e p a r a l l e l a n d s e r i e s h yb r i d s . T h e s e r e g e n g r o u p s
strictly are design topologies for braking systems. It also matters how m a n y w h e e l s y o u a r e u s i n g t o r e c l a i m e n e r g y. M o s t v e h i c l e s t o d a t e a r e front wheel drive so you can only reclaim energy from the front wheels. The back wheels still waste energy to standard friction brakes u n l e s s t h e y a r e s o m e h o w c o n n e c t e d b a c k t o t h e e l e c t r i c m o t o r. T h e o t h e r f a c t o r i s b a t t e r y s t a t e o f c h a r g e a n d h o w h a r d c a n yo u d r i v e t h a t e n e r g y b a c k i n t o t h e b a t t e r y.
C H A P T E R 7: CONCLUSION Theoretical investigations of a regenerative braking system show about 25% saving in fuel consumption. The lower operating and environment costs of a vehicle with regenerative braking system should make it more attractive than a conventional
one.
The
traditional
cost
of
the
s ys t e m
could
be
r e c o v e r e d i n t h e f e w y e a r s o n l y. The exhaust emission of vehicle using the regenerative braking concept would be much less than equivalent conventional vehicles as less fuel are used for consumption. These systems are particularly suitable in developing countries such as India where buses are the preferred means of transportation within the cities.
BIBLIOGRAPHY 1 ) G e n e r a l M o t o r s Web s i t e ( w w w .g m . c o m ) . 2 ) w w w .s a e . o r g 3 ) w w w .g o o g l e . c o m
SUBMITTED BY:
GUIDED BY: -
ACKNOWLEDGEMENT This acknowledgement is a humble attempt to earnestly thank all those who were directly or indirectly involved in preparation of this seminar report. I n p a r t i c u l a r I a m t h a n k f u l t o m y g u i d e M r. K a l p e s h D . M a n i a who guide me in my seminar work. I am thankful to him for taking active part in the preparation of my seminar report. It was impossible to present this report without his co-operation and suggestion.
Last but not least I would like to express out deep sense of gratitude
to
all
the
faculty
of
Mechanical
Engineering
Department and also my friends who help me to accomplish what I have s t a r t e d f o r.
DEPARTMENT OF MECHANICAL ENGINEERING THE SEMINAR REPORT ON :
REGENERATIVE BRAKING SYSTEM PREPARED BY: GUIDED BY: EXAMINER
H.O.D
(1) ___________________ (2) ___________________ (3) ___________________ (4) ___________________
ABSTRACT Regenerative Braking System is the way of slowing vehicle by using the motors as brakes.
Instead of the surplus energy of the vehicle
being wasted as unwanted heat, the motors act as generators and return s o m e o f i t t o t h e o v e r h e a d w i r e s a s e l e c t r i c i t y. The vehicle is primarily powered from the electrical energy generated from the generator, which burns gasoline.
This energy is stored in a
l a r g e b a t t e r y, a n d u s e d b y a n e l e c t r i c m o t o r t h a t p r o v i d e s m o t i v e f o r c e to the wheels. The regenerative barking taking place on the vehicle is a way to obtain more efficiency; instead of converting kinetic energy to thermal energy through frictional braking, the vehicle can convert a g o o d f r a c t i o n o f i t s k i n e t i c e n e r g y b a c k i n t o c h a r g e i n t h e b a t t e r y, u s i n g t h e s a m e p r i n c i p l e a s a n a l t e r n a t o r.
LIST OF FIGURES Fig. 1
G r a p h i c a l r e p r e s e n t a t i o n o f e n e r g y u s a g e b e t w e e n t w o v e h i c l e s.
Fig. 2
Mercury Hybrid Mariner
Fig. 3
R e g e n e r a t i v e B r a k i n g S ys t e m U s i n g N i t i n o l S p r i n g .
CONTENTS
1. INTRODUCTION 2. NECESSITY OF THE SYSTEM 3. REGENRATIVE BRAKE 4. ELEMENTS OF THE SYSTEM 5. DESCRIPTION & OPERATION 6. RESULTS 7. CONCLUSION
CHAPTER 1: INTRODUCTION
Brake:A brake is a machine element and its principle object is to absorb energy during deceleration.
In vehicle brakes are used to absorb
kinetic energy whereas in hoists or elevators brakes are also used to absorb
potential
stationary frame, e n e r g y.
e n e r g y. normally
By
connecting
the
brake converts
moving
kinetic
member
energy to
to
heat
This causes wastage of energy and also wearing of frictional
lining material. Regenerative Braking System:Regenerative Braking System is the way of slowing vehicle by using the motors as brakes.
Instead of the surplus energy of the
vehicle being wasted as unwanted heat, the motors act as generators a n d r e t u r n s o m e o f i t t o t h e o v e r h e a d w i r e s a s e l e c t r i c i t y. The vehicle is primarily powered from the electrical energy generated from the generator, which burns gasoline.
This energy is stored in a
l a r g e b a t t e r y, a n d u s e d b y a n e l e c t r i c m o t o r t h a t p r o v i d e s m o t i v e f o r c e to the wheels. The regenerative barking taking place on the vehicle is a way to obtain more efficiency; instead of converting kinetic energy to
thermal energy through frictional braking, the vehicle can convert a g o o d f r a c t i o n o f i t s k i n e t i c e n e r g y b a c k i n t o c h a r g e i n t h e b a t t e r y, u s i n g t h e s a m e p r i n c i p l e a s a n a l t e r n a t o r. T h e r e f o r e , i f yo u d r i v e l o n g d i s t a n c e w i t h o u t b r a k i n g , yo u ’ l l b e powering the vehicle entirely from gasoline. The regenerative braking Regenerative Braking System comes into its own when you’re driving i n t h e c i t y, a n d s p e n d i n g a g o o d d e a l o f yo u r t i m e b r a k i n g . You w i l l s t i l l u s e m o r e f u e l i n t h e c i t y f o r e a c h m i l e yo u d r i v e t h a n o n t h e h i g h w a y, t h o u g h . ( T h e r m o d y n a m i c s t e l l s u s t h a t a l l i n e f f i c i e n c y c o m e s f r o m h e a t g e n e r a t i o n . F o r i n s t a n c e , w h e n yo u b r a k e , t h e b r a k e p e d a l s h e a t u p a n d a q u a n t i t y o f h e a t , o r e n e r g y, i s l o s t t o t h e o u t s i d e w o r l d . F r i c t i o n i n t h e e n g i n e p r o d u c e s h e a t i n t h e s a m e w a y. Heat
e n e r g y,
also,
has
higher
entropy
than,
s a y,
electric,
meaning that it is less ordered.) Definition: Braking method in which the mechanical energy from the load is converted into electric energy and regenerated back into the line is known as Regenerative Braking.
The Motor operates as
g e n e r a t o r. R e g e n e r a t i v e B r a k i n g F o r H y b r i d Veh i c l e : I n m o s t e l e c t r i c a n d h y b r i d e l e c t r i c v e h i c l e s o n t h e r o a d t o d a y, t h i s i s a c c o m p l i s h e d b y o p e r a t i n g t h e t r a c t i o n m o t o r a s a g e n e r a t o r, providing braking torque to the wheels and recharging the traction batteries.
The energy provided by regenerative braking can then be
used for propulsion or to power vehicle accessories.
CHAPTER 2: NECESSITY OF THE SYSTEM The regenerative braking system delivers a number of significant advantages over a car that only has friction brakes. In low-speed, stopand-go traffic where little deceleration is required; the regenerative braking system can provide the majority of the total braking force. This vastly improves fuel economy with a vehicle, and further enhances the attractiveness of vehicles using regenerative braking for city d r i v i n g . At h i g h e r s p e e d s , t o o , r e g e n e r a t i v e b r a k i n g h a s b e e n s h o w n t o contribute to improved fuel economy – by as much as 20%. Consider a heavy loaded truck having very few stops on the road. I t i s o p e r a t e d n e a r m a x i m u m e n g i n e e f f i c i e n c y. T h e 8 0 % o f t h e e n e r g y produced is utilized to overcome the rolling and aerodynamic road forces.
The energy wasted in applying brake is about 2%.
Al s o i t s
brake specific fuel consumption is 5%. Now consider a vehicle, which is operated in the main city where t r a f f i c i s a m a j o r p r o b l e m h e r e o n e h a s t o a p p l y b r a k e f r e q u e n t l y. F o r such vehicles the wastage of energy by application of brake is about 60% to 65%.
An d a l s o i t i s i n e f f i c i e n t a s i t s b r a k e s p e c i f i c f u e l
consumption is high.
Road 80%
Rake 65% Other 18%
Brake 2%
HEAVY LOADED TRUCK
Road 26% other 9%
CITY BUS
2.1 Graphical representation of energy usage between two vehicles.
S o me
of
the
a d v an t a g e s
of
reg e n e r a t i v e
b r a ki n g
over
c o n v e n t i o n a l b r a ki n g a re a s f o l l ow s : Energy Conservation: T h e f l yw h e e l a b s o r b s e n e r g y w h e n b r a k i n g v i a a c l u t c h s ys t e m s l o w i n g t h e c a r d o w n a n d s p e e d i n g u p t h e w h e e l . To a c c e l e r a t e , a n o t h e r c l u t c h s ys t e m c o n n e c t s t h e f l yw h e e l t o t h e d r i v e t r a i n , s p e e d i n g u p t h e c a r a n d s l o w i n g d o w n t h e f l yw h e e l .
Energy is therefore conserved rather than
wasted as heat and light which is what normally happens in the c o n t e m p o r a r y s h o e / d i s c s ys t e m . Wea r R e d u c t i o n : An electric drive train also allows for regenerative breaking which increases Efficiency and reduces wear on the vehicle brakes.
In
regenerative raking, when the motor is not receiving power from the battery pack, it resists the turning of the wheels, capturing some of the energy of motion as if it were a generator and returning that energy to the battery pack.
In mechanical brakes; lessening wear and extending
brake life is not possible. This reduces the use of use the brake. Fuel Consumption: The fuel consumption of the conventional vehicles and regenerative b r a k i n g s ys t e m v e h i c l e s w a s e v a l u a t e d o v e r a c o u r s e o f v a r i o u s f i x e d urban driving schedules. The results are compared as shown in figure. R e p r e s e n t i n g t h e s i g n i f i c a n t c o s t s a y i n g t o i t s o w n e r, i t h a s b e e n proved the regenerative braking is very fuel-efficient. Braking is not total loss: C o n v e n t i o n a l b r a k e s a p p l y f r i c t i o n t o c o n v e r t a v e h i c l e ’s k i n e t i c e n e r g y into heat. In energy , therefore, braking is a total loss: once heat is generated, it is very difficult to reuse.
The regenerative braking
s ys t e m , h o w e v e r, s l o w s a v e h i c l e d o w n i n a d i f f e r e n t w a y.
CHAPTER 3 :REGENERATIVE BRAKING SYSTEM . A regenerative brake is an apparatus, a device or system which allows a vehicle to recapture and store part of the kinetic energy that would otherwise be 'lost' to heat when braking.
The IMA operating principle
Honda's patented IMA concept is quite simple - use an efficient Otto engine supplemented by an electric motor when additional power is n e e d e d . Al s o r e f e r r e d t o a s a ' h yb r i d ' s ys t e m b e c a u s e i t u s e s t w o p o w e r s o u r c e s , t h e I M A c o n c e p t a l l o w s t h e C i v i c H yb r i d t o u s e a s m a l l e r gasoline engine without any significant loss in performance.
T h i s s ys t e m i s e s p e c i a l l y e f f e c t i v e d u e t o t h e f a c t t h a t a c c e l e r a t i o n requires a significantly higher power than needed for cruising on a level r o a d ( w h e r e v e h i c l e s s p e n d m o s t o f t h e i r t i m e ) . An e n g i n e m o r e powerful than needed has to work under low load most of the time, condition where its efficiency is lower than under high loads, thus w o r s e n i n g t h e v e h i c l e ' s f u e l e c o n o m y..
The electric motor-generator positioned between the engine and transmission assists the engine when accelerating and recovers energy to store in batteries when braking or decelerating (regenerative braking), allowing it to operate independently without the need for a grid power s u p p l y. W h e n t h e C i v i c H yb r i d i s c o a s t i n g o r i t s b r a k e s a r e a p p l i e d , i t s e l e c t r i c m o t o r b e c o m e s a g e n e r a t o r, c o n v e r t i n g f o r w a r d m o m e n t u m ( k i n e t i c e n e r g y) i n t o e l e c t r i c a l e n e r g y, i n s t e a d o f w a s t i n g i t a s h e a t d u r i n g conventional braking. Energy is stored in a battery pack located behind t h e r e a r s e a t i n t h e t r u n k . I f t h e s t a t e o f c h a r g e o f t h e b a t t e r i e s i s l o w, the motor-generator will also recharge them while the Civic Hybrid is cruising.
CHAPTER 4: ELEMENTS OF THE SYSTEM There are three basic element required which are necessary for the working of regenerative braking system, these are : 1.Energy Storage Unit (ESU): The ESU performs two primary functions 1.TO recover & store braking energy 2. TO absorb excess engine energy during light load operation The selection criteria for an effective energy storage includes 1. High specific energy storage density 2. High energy transfer rate 3. Small space requirement The energy recaptured by regenerative braking might be stored in one of
three
devices:
an
electrochemical
b a t t e r y,
a
f l yw h e e l ,
in
a
regenerative fuel cell. Regen and Batteries: Wi t h t h i s s ys t e m , t h e e l e c t r i c m o t o r o f a c a r b e c o m e s a g e n e r a t o r w h e n the brake pedal is applied. The kinetic energy of the car is used to g e n e r a t e e l e c t r i c i t y t h a t i s t h e n u s e d t o r e c h a r g e t h e b a t t e r i e s . Wit h t h i s s ys t e m , t r a d i t i o n a l f r i c t i o n b r a k e s m u s t a l s o b e u s e d t o e n s u r e t h a t t h e c a r s l o w s d o w n a s m u c h a s n e c e s s a r y. T h u s , n o t a l l o f t h e k i n e t i c energy of the car can be harnessed for the batteries because some of it is "lost" to waste heat. Some energy is also lost to resistance as the energy travels from the wheel and axle, through the drivetrain and e l e c t r i c m o t o r, a n d i n t o t h e b a t t e r y. F o r e x a m p l e , t h e Toyo t a P r i u s c a n o n l y r e c a p t u r e a b o u t 3 0 % o f t h e v e h i c l e s k i n e t i c e n e r g y. The Honda Insight is another vehicle in addition to the Prius that is on the market and currently uses regenerative braking. In the Insight there are two deceleration modes: When the throttle is engaged, but the brake
p e d a l i s n o t , t h e v e h i c l e s l o w s d o w n g r a d u a l l y, a n d t h e b a t t e r y r e c e i v e s a partial charge.
When the brake pedal is depressed, the battery receives a higher c h a r g e , w h i c h s l o w s t h e v e h i c l e d o w n f a s t e r. T h e f u r t h e r t h e brake pedal is depressed, the more the conventional friction brakes are employed.
I n t h e I n s i g h t , t h e m o t o r / g e n e r a t o r p r o d u c e s AC , w h i c h i s c o n v e r t e d into DC, which is then used to charge the Battery Module. The Insight, a s w e l l a s a l l o t h e r r e g e n e r a t i v e s ys t e m s , m u s t h a v e a n e l e c t r i c controller that regulates how much charge the battery receives and how much the friction brakes are used. Regen and Flywheels: I n t h i s s ys t e m , t h e t r a n s l a t i o n a l e n e r g y o f t h e v e h i c l e i s t r a n s f e r r e d i n t o r o t a t i o n a l e n e r g y i n t h e f l yw h e e l , w h i c h s t o r e s t h e e n e r g y u n t i l i t i s n e e d e d t o a c c e l e r a t e t h e v e h i c l e . T h e b e n e f i t o f u s i n g f l yw h e e l technology is that more of the forward inertial energy of the car can be captured than in batteries, because the flywheel can be engaged even during relatively short intervals of braking and acceleration. In the case of batteries, they are not able to accept charge at these rapid i n t e r v a l s , a n d t h u s m o r e e n e r g y i s l o s t t o f r i c t i o n . An o t h e r a d v a n t a g e of flywheel technology is that the additional power supplied by the f l yw h e e l
during
acceleration
substantially
supplements
the
o u t p u t o f t h e s m a l l e n g i n e t h a t h yb r i d v e h i c l e s a r e e q u i p p e d w i t h .
power
2 . C o n t i n u o u s l y Var i a b l e Tra n s m i s s i o n ( C V T ) : The energy storage unit requires a transmission that can handle torque and speed demands in a steeples manner and smoothly control energy flow to and from the vehicle wheels. continuously
variable
transmission
and
F o r t h e f l yw h e e l t h e
vehicle
because
flywheel
rotational speed increases when vehicle speed decreases and vice versa. F l yw h e e l c a n w o r k w e l l w i t h e i t h e r m e c h a n i c a l o r h yd r o s t a t i c continuously variable transmission. 3. Control System : An “ON-OFF” engine control system is used. That means that the engine is “ON” until the energy storage unit has been reached the desired charge capacity and then is decoupled and stopped until the energy storage unit charge fall below its minimum requirement.
C H A P T E R 5 : DESCRIPTION & OPERATION How regenerative braking system works? R e g e n e r a t i v e ( o r D yn a m i c B r a k i n g ) o c c u r s w h e n t h e v e h i c l e i s i n motion, such as coasting, traveling downhill or braking. accelerator pedal is not being depressed.
An d t h e
During “Regent,” the motor
becomes a generator and sends energy back to the batteries. It is explained as follows, because the wheels of a decelerating vehicle are still moving forward, they can be made to turn the electric m o t o r, w h i c h t h e n f e e d s e n e r g y t o t h e b a t t e r i e s f o r s t o r a g e . T h e s ys t e m b e c o m e s , i n e f f e c t , a g e n e r a t o r, w h i c h p r o v i d e s b r a k i n g f o r c e w h i l e i t c o n v e r t s t h e v e h i c l e ’s k i n e t i c e n e r g y i n t o a r e u s a b l e f o r m - e l e c t r i c a l e n e r g y. When the accelerator pedal is released, the absence of pressure triggers a response from the Energy Storage Unit (ESU).
Regenerative
braking begins, and the batteries are re-charged by the motor, which is turned by the wheels. In this case, the friction brakes are not engaged. If more vigorous deceleration is required, and the brake pedal is depressed, this engages both sets of brakes.
H o w e v e r, t o m a x i m i z e
e n e r g y e f f i c i e n c y, i t i s a d v a n t a g e o u s t o a p p l y t h e r e g e n e r a t i v e b r a k e a s such as possible – it therefore tends to do more of its total work in the first part of the braking motion. There are two deceleration modes: 1. Foot off throttle but not on brake pedal – in this mode, the charge/assist gauge will show partial charge, and the vehicle will slow d o w n g r a d u a l l y.
2. Foot on brake pedal - In this mode, a higher amount of regeneration w i l l b e a l l o w e d , a n d t h e v e h i c l e w i l l s l o w m o r e r a p i d l y.
During light
brake pedal application, only the IMA motor//generator is slowing the c a r.
Wit h h e a v i e r b r a k e p e d a l a p p l i c a t i o n , t h e c o n v e n t i o n a l f r i c t i o n
b r a k e s a l s o c o m e i n t o p l a y. W h e n d e c e l e r a t i n g , r e g e n e r a t i o n w i l l c o n t i n u e u 8 n t i l e n g i n e s p e e d f a l l s t o a b o u t 1 0 0 0 r p m . At t h i s p o i n t , t h e driver will typically shift into neutral.
EXAMPLE
Mercury Hybrid Mariner 1. Mercury Mariner Hybrid P r o d u c t i o n P u l l a h e a d : P r o d u c t i o n b e g i n s a ye a r ahead of schedule Growing the Mercury Brand: New models and goals Distinctive Design: Mariner features clean lines, careful craftsmanship P o w e r P l a y : F u l l - h yb r i d g a s o l i n e a n d e l e c t r i c p o w e r t r a i n D yn a m i c C h a s s i s : N i m b l e h a n d l i n g a n d a s m o o t h , q u i e t r i d e Distinguished Safety: Full array of safety features Green Mission: Ford Motor Company's strategy for sustainability in vehicles T h e M e r c u r y M a r i n e r H yb r i d o f f e r s a u n i q u e l y s a t i s f yi n g t r a n s p o r t a t i o n choice for an ever-increasing segment of the population concerned about the environment. It's a stylish, upscale sport-utility vehicle with nimble handling and impressive performance, as well as ample cargo a n d t o w i n g c a p a c i t y. I n a d d i t i o n , i t ' s a n e n v i r o n m e n t a l l y c o n s c i o u s SUV with remarkable fuel economy – an estimated 33 miles per gallon ( m p g ) c i t y, 2 9 m p g h i g h w a y – a n d i s e x p e c t e d t o m e e t t h e c l e a n e s t emissions rating achievable by a fossil-fuel vehicle (California's A d v a n c e d Tec h n o l o g y P a r t i a l Z e r o E m i s s i o n s Veh i c l e s t a n d a r d ) .
Engineers placed the additional hybrid powertrain components low and t o t h e r e a r, t o l o w e r t h e c e n t e r o f g r a v i t y a n d i m p r o v e t h e c o n v e n t i o n a l Mariner's front-rear weight distribution. The rack-and-pinion steering is electrically assisted, rather than using t h e t r a d i t i o n a l h yd r a u l i c s t e e r i n g p u m p f o r c o n s i s t e n t s t e e r i n g e f f o r t s and control whether the gasoline engine is stopped or running. Regenerative braking uses the traction motor to assist the four-wheel disc brakes in slowing Mariner Hybrid while simultaneously generating e l e c t r i c i t y f o r c h a r g i n g t h e b a t t e r y.
R e g e n e r a t i v e b r a k i n g o f Toy o t a P r i u s : Toyo t a r e a l i z e d t h a t o n e w a y t o a c h i e v e l o n g e r v e h i c l e r a n g e w a s
to conserve and reuse some of the energy that a vehicle normally loses as heat caused by braking friction. This idea led engineers to apply the principles of regenerative braking. I n a l l Toy o t a v e h i c l e s t h a t f e a t u r e t h e r e g e n e r a t i v e b r a k i n g s ys t e m , t h e r e g e n e r a t i v e b r a k e i s o n l y r e s p o n s i b l e f o r a p a r t o f t h e deceleration necessary to stop the vehicle.
I n a n E V, t h i s f r a c t i o n i s
d e t e r m i n e d b y t h e v e h i c l e ’s s p e e d w h e n b r a k i n g i s i n i t i a t e d .
The
r e m a i n i n g b r a k i n g f o r c e i s p r o v i d e d b y t h e v e h i c l e ’s f r i c t i o n b r a k e s . To m a x i m i z e f u e l e c o n o m y, o f c o u r s e , t h e r e g e n e r a t i v e b r a k i n g s ys t e m is made to do as much of the braking work as possible.
C o m p o n e n t U s e d i n Toy o t a P r i u s f o r R e g e n e r a t i v e B r a k i n g S y s t e m : Brake Pedal: I t i s u s e d t o a p p l y b r a k i n g f o r c e b y t h e d r i v e r. Hydraulic Booster Unit: I t i s c o m p o s e d o f t h e m a s t e r c y l i n d e r a n d t h e r e g u l a t o r, r e s p o n d s i n two steps. First it signals electronically to the brake ECU that braking force has been demanded. pressure
on
the
pedal
Next, the master cylinder exerts hydraulic
stroke
simulator,
and
the
regulator
feeds
h yd r a u l i c f l u i d t o t h e h yd r a u l i c p r e s s u r e c o n t r o l u n i t . Brake ECU: The brake ECU senses the braking demand and sends a fraction of this demand to the THSECU for regenerative braking. It also calculates the force necessary to fulfill remaining braking demand and instruct the hydraulic pressure control unit to on a corresponding amount of hydraulic fluid Pedal Stroke Simulator: I t a b s o r b s a n a m o u n t o f h yd r a u l i c p r e s s u r e f r o m m a s t e r c y l i n d e r t h a t corresponds to the amount of braking force applied by the regenerative braking system. A s h yd r a u l i c p r e s s u r e i s f e d b a c k t o t h e p e d a l , t h e p e d a l , t h e p e d a l s t r o k e s i m u l a t o r f e e d s b a c k t o t h e m a s t e r c yl i n d e r.
T H S ( Toy o t a H y b r i d S y s t e m ) E C U : It induces regenerative braking, and returns a signal that indicates braking force output back to the brake ECU. Hydraulic Pressure Control Unit: It es on a corresponding amount of hydraulic fluid to a four way c yl i n d e r.
C H A P T E R 6: R E S U LT Regenerative
braking
technology
is
one
more
positive
step
f o r w a r d i n Toyo t a ’s q u e s t t o r e a l i z e t h e u l t i m a t e e c o c a r. B y w o r k i n g i n concert with previously developed electric motor technologies, its application
helps
Toyo t a ’s
electric
vehicles
and
h yb r i d
vehicles
(including the recently released prius) to achieve extended ranges and t o b e f r i e n d l i e r t o t h e e n v i r o n m e n t t h a n e v e r b e f o r e . At t h e s a m e t i m e , this new technology remains unobtrusively in the background; drivers b e n e f i t f r o m r e g e n e r a t i v e b r a k i n g w h i l e e n j o yi n g t h e s a m e f i r m b r a k i n g feel found in conventionally equipped vehicles.
Wheel Rotating Device.
Wheel – A Rotating Device – B Shafts – C.D. Gearbox –E Clutch – G Spring - H
Shafts.
Gearbox
Clutch
Spring
7.1 Regenerative braking system using Nitinol Spring
A hydraulic regenerative braking system improves the fuel economy of Ford's F-350 Tonka 25-35% during stop-andgo driving. The system provides power during initial acceleration when demand peaks.
T h e H L A s y s t e m c o n s i s t s o f a r e v e r s i b l e h yd r a u l i c p u m p / m o t o r f r o m Eaton's Fluid Power Group (Eden Prairie, MN) coupled to the drive s h a f t t h r o u g h a c l u t c h a n d t w o a c c u m u l a t o r s . As t h e d r i v e r s t e p s o n t h e brake, the pump/motor forces hydraulic fluid out of a low-pressure a c c u m u l a t o r a n d i n t o a h i g h - p r e s s u r e a c c u m u l a t o r, i n c r e a s i n g t h e pressure of nitrogen gas stored there to 5,000 psi. D u r i n g a c c e l e r a t i o n , t h e H L A s ys t e m s w i t c h e s f r o m t h e p u m p m o d e t o t h e m o t o r m o d e , t h e n i t r o g e n g a s f o r c e s t h e h yd r a u l i c f l u i d b a c k i n t o t h e l o w - p r e s s u r e a c c u m u l a t o r, a n d t h e p u m p / m o t o r a p p l i e s t o r q u e t o t h e driveshaft through the clutch. If quick acceleration is required, the F3 5 0 ' s d i e s e l e n g i n e w o r k s w i t h t h e H L A s ys t e m
T h e h y d r a u l i c l a u n c h a s s i s t s y s t e m i n t h e F - 3 5 0 Ton k a f u n c t i o n s a s a secondary source of energy during peak power demand. It consists of a low-pressure accumulator in blue, and a high-pressure accumulator in r e d . T h e s y s t e m c a p t u r es e n e r g y n o r m a l l y d i s s i p a t e d a s h e a t d u r i n g b r e a k i n g , s t o r es i t , a n d u s e s i t l a t e r d u r i n g p e r i o d s o f p e a k p o w e r demand. Eighty percent of the initial kinetic energy is returned to the vehicle. " T h e s y s t e m s t o r e s a p p r o x i m a t e l y 3 8 0 k J o f e n e r g y," s a ys B r a d Bohlmann, a mechanical engineer and business development c o o r d i n a t o r i n Ad v a n c e d Tec h n o l o g y a t E a t o n ' s F l u i d P o w e r G r o u p . " Wi t h t h a t m u c h e n e r g y, w e c a n a c c e l e r a t e a 1 0 , 0 0 0 - l b v e h i c l e f r o m a dead stop to between 25 and 30 miles per hour with no assistance from the vehicle's combustion engine." "Ford thinks that both electric and hydraulic regenerative systems have a f u t u r e , " s a ys J o h n B r e v i c k , a F o r d m e c h a n i c a l e n g i n e e r w o r k i n g o n the HLA system. "But for heavy vehicles like our 10,000-lb F-350 trucks, hydraulics are better at capturing lost energy than electric s ys t e m s . " Eaton's Bohlmann explains that the real advantage of hydraulics is in i t s p o w e r d e n s i t y. " H y d r a u l i c s i s c a p a b l e o f t r a n s f e r r i n g e n e r g y v e r y q u i c k l y," s a ys B o h l m a n n . " T h e r a t e o f e n e r g y t r a n s f e r i s i n a h y b r i d e l e c t r i c s ys t e m o f a s i m i l a r s i z e i s m u c h l o w e r." Bohlmann adds that the specific vocation or driving cycle of the v e h i c l e d e t e r m i n e s w h e t h e r a h y b r i d h yd r a u l i c o r h yb r i d e l e c t r i c s y s t e m is best suited for the vehicle. "Think of hydraulics as a sprinter,
p r o v i d i n g f a s t b u r s t s o f p o w e r," h e s a ys . " A n e l e c t r i c h yb r i d i s m o r e l i k e a m a r a t h o n r u n n e r." " T h e c h a l l e n g e n o w i s t o m a k e u s e o f t h e r e g e n e r a t i v e b r a k i n g s ys t e m s e a m l e s s t o t h e c u s t o m e r ," s a y s F o r d ' s B r e v i c k . " We s t i l l h a v e r o o m f o r i m p r o v e m e n t s a n d f e e l t h e H L A s ys t e m h a s a l o t o f p o t e n t i a l . " As for the future, Ford, Eaton, and the U.S. Environmental Protection A g e n c y ( E PA) a r e j o i n t l y c o n d u c t i n g r e s e a r c h o n h y d r a u l i c h yb r i d vehicles, including internal combustion engines that would produce h yd r a u l i c p r e s s u r e t o d r i v e t h e v e h i c l e . E a t o n s i g n e d b o t h a t e c h n o l o g y license agreement and a cooperative research and development a g r e e m e n t w i t h t h e E PA f o r t h e d e v e l o p m e n t o f f u t u r e g e n e r a t i o n s ys t e m s . Inertia, Force and Mass E v e r yt h i n g h a s i n e r t i a ; i f i t h a s a m a s s , i t h a s i n e r t i a . A h y b r i d r e c l a i m s e n e r g y t h r o u g h t h e f u n d a m e n t a l s o f p h ys i c s . D o yo u r e m e m b e r any high school or college physics? You a p p l y a f o r c e t o m o v e a n o b j e c t . T h e e q u a t i o n f o r t h i s i s : F=ma “F” being the force, “m” being the mass and “a” being the acceleration The faster you want an object to accelerate, the more force you have to a p p l y. L e t ’s j u s t l o o k a t t h e e l e c t r i c m o t o r f o r n o w. E n e r g y f r o m t h e b a t t e r y ( Wat t s ) i s a p p l i e d t o t h e c o i l w i n d i n g s i n t h e m o t o r. T h e s e w i n d i n g s then produce a magnetic force on the rotor of the motor, which produces torque on the output shaft. This torque is then applied to the wheels of the car via a coupling of gears and shafts. When the wheel turns, it applies a force to the ground, which due to friction between the wheel and the ground causes the vehicle to move along the surface. T h i s i s l i k e i f yo u w e r e i n a b o a t a t a d o c k , a n d y o u g r a b b e d t h e d o c k a n d p u s h e d w i t h yo u r a r m . T h e f o r c e y o u a r e g e n e r a t i n g i s m o v i n g t h e b o a t r e l a t i v e t o t h e l o c a t i o n o f t h e d o c k . T h e m o r e f o r c e y o u a p p l y, t h e f a s t yo u g e t t h e b o a t t o m o v e . Friction in Hybrids T h e r e i s f r i c t i o n e v e r yw h e r e i n t h e h y b r i d s ys t e m . T h e r e i s e l e c t r i c a l friction between the atoms and electrons moving in the wires between the battery and the motor and through the motor itself. There is magnetic friction in the metal laminations that make up the magnetic
circuit of the motor, as well as in the magnets again on the atomic level. Then, there is mechanical friction between every moving part, s u c h a s t h e b e a r i n g s , s e a l s , g e a r s , c h a i n s a n d s o o n . T h e b y- p r o d u c t o f f r i c t i o n i s h e a t . Tak e y o u r h a n d s r u b t h e m t o g e t h e r a n d yo u r p a l m s g e t w a r m . T h e f a s t e r y o u d o i t , t h e f a s t e r t h e y h e a t u p . Al s o , t h e h a r d e r they are pressed together, the faster they will heat. Friction is energy lost to heat. When all of these losses are added up, that is what determines the efficiency of the vehicle. Frictional Losses in Conventional Cars A standard car generates torque to move the wheels to drive the vehicle down the road. During this time, it is generating friction and losses. W h e n yo u a p p l y s t a n d a r d b r a k e s , i t i s j u s t a n o t h e r f r i c t i o n d e v i c e t h a t has specially designed material to handle the heat from friction, which is applied to the drums and rotors that stop the wheel from turning. The friction between the wheel and the ground stops the vehicle. This standard vehicle has frictional losses to move the vehicle—and uses the f u n d a m e n t a l b e h i n d f r i c t i o n a l l o s s e s t o s t o p t h e v e h i c l e . S o i t ’s a l o s e lose situation. Tra n s f e r r i n g Tor q u e B a c k t o t h e M o t o r This inertia is the fundamental property of physics that is used to reclaim energy from the vehicle. Instead of using 100% of the foundation brakes of the vehicle, which are the friction brakes, we now let the linkages back to the motor such as the drive shafts, chains, and gears transfer the torque from the wheels back into the motor shaft. One of the unique things about most electric motors is that electrical energy can be transferred into mechanical energy and also mechanical e n e r g y c a n b e t r a n s f e r r e d b a c k i n t o e l e c t r i c a l e n e r g y. I n b o t h c a s e s , t h i s c a n b e d o n e v e r y e f f i c i e n t l y. T h u s , t h r o u g h t h e t e c h n o l o g y o f t h e m o t o r a n d m o t o r c o n t r o l l e r, t h e force at the wheels becomes torque on the electric motor shaft. The magnets on the shaft of the motor (called the rotor—the moving part of the motor) move past the electric coils on the stator (the stationary part of the motor) ing the magnetic fields of the magnets through the c o i l s p r o d u c i n g e l e c t r i c i t y. T h i s e l e c t r i c i t y b e c o m e s e l e c t r i c a l e n e r g y, w h i c h i s p u m p e d b a c k t o t h e b a t t e r y. T h i s , i n t u r n , c h a r g e s t h e h yb r i d battery pack. This is where the comment “regeneration” or “reclaiming e n e r g y” c o m e s f r o m . T h a t i s t h e b a s i c s o f h o w r e g e n e r a t i o n w o r k s . H o w m u c h e n e r g y yo u can reclaim depends on a lot of factors. There are different regeneration theories and designs, which fall into two groups: one being called parallel regen and the other called series regen, which are d i f f e r e n t f r o m t h e p a r a l l e l a n d s e r i e s h yb r i d s . T h e s e r e g e n g r o u p s
strictly are design topologies for braking systems. It also matters how m a n y w h e e l s y o u a r e u s i n g t o r e c l a i m e n e r g y. M o s t v e h i c l e s t o d a t e a r e front wheel drive so you can only reclaim energy from the front wheels. The back wheels still waste energy to standard friction brakes u n l e s s t h e y a r e s o m e h o w c o n n e c t e d b a c k t o t h e e l e c t r i c m o t o r. T h e o t h e r f a c t o r i s b a t t e r y s t a t e o f c h a r g e a n d h o w h a r d c a n yo u d r i v e t h a t e n e r g y b a c k i n t o t h e b a t t e r y.
C H A P T E R 7: CONCLUSION Theoretical investigations of a regenerative braking system show about 25% saving in fuel consumption. The lower operating and environment costs of a vehicle with regenerative braking system should make it more attractive than a conventional
one.
The
traditional
cost
of
the
s ys t e m
could
be
r e c o v e r e d i n t h e f e w y e a r s o n l y. The exhaust emission of vehicle using the regenerative braking concept would be much less than equivalent conventional vehicles as less fuel are used for consumption. These systems are particularly suitable in developing countries such as India where buses are the preferred means of transportation within the cities.
BIBLIOGRAPHY 1 ) G e n e r a l M o t o r s Web s i t e ( w w w .g m . c o m ) . 2 ) w w w .s a e . o r g 3 ) w w w .g o o g l e . c o m
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