Hybrid Electric Bike Research

Documentation of Research for a Hybrid Electric Bicycle

Inter-professional Inter-professional Project 315 Spring 2003 Written by: Leo Carrera, Seung Il Choi, George Derrick, Shaun Diggs, Darius Dubanski, Waqas Jamal, Kitae Kim, Kylie Klint, Jeongwoo Lee, Leonard Nelson, Michael George, Sungwoo Min, and Ryan S Lim.

IPRO 315 – HYBRID ELECTRIC BICYCLE

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Table of Contents

Subject

Page

Introduction to IPRO 315

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Hybrid Drive Train Configurations

X

Chain Drive vs. Shaft Drive

X

Permanent Magnet Motors vs. No Magnets

X

Variable air gaps within a motor

X

Power Splitter

X

Regenerative Braking

X

Controllers

X

Batteries

X

Concluding Results

X


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Introduction to IPRO 315 Kylie R. KLINT Abstract — Inter-professional Project 315 (IPRO 315) is a group of students set up to research and and desi design gn a hybr hybrid id elec electr tric ic bicy bicycl cle. e. With With a wide wide vari variet ety y of stud studen ents ts, , all all comi coming ng from from different areas of studies, everyone is able to bring good ideas to the drafting table. In this publi publicat cation ion, , many many differ different ent concep concepts ts will will be explor explored ed regard regarding ing the actual actual design design of the bicycle, the different types of motors, various batteries, regenerative braking, and methods for controlling the complete apparatus. Conclusions were drawn from each theory investigated determining whether they should be implemented in a prototype or set aside for a different design.

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UCH discussion was given to how far back this IRPO should start, meaning shall IPRO 315 design an entirely new bicycle, or shall a bicycle frame, already built, be used and and the the nece necess ssar ary y comp compon onen ents ts adde added d to it? it? To deci decide de upon upon this this, , two two diff differ eren ent t mechanical designs, parallel and serial, will be explored as well as different types of drive drive shafts. shafts. Various Various drive drive shafts shafts ultimat ultimately ely determi determine ne the overall overall mechanic mechanical al efficiency of the bicycle. If a chain drive is used, then assorted gearing styles also affect the mechanical efficiency and in turn influence the motor. Ther There e are are many many, , many many moto motors rs on the the mark market et toda today, y, but but a sele select ct few few fit fit this this appli applicat catio ion. n. A motor motor can can be purcha purchase sed d in a motor motor/g /gene enera rator tor set or the the motor motor and generator generator separately. In order to establish establish a type of motor, research must be done to decide upon the generation system. Ranges of diverse batteries also carry some advantages and disadvantages. By using resources available to us on the IIT campus, IPRO 315 shall settle on which type of battery is the most excellent battery for this application considering size, weight, current output, and discharge time. Again, investigating the knowledge held within these school walls, a controller shall be designed for IPRO 315 specifications and implemented in a prototype managing both the motor and generator. As a starting point for the IRPO 315 research, the different designs of both hybrid electric electric bicycles bicycles and electri electric c bicycles bicycles on the market today will be examined examined and scrutinized. Out of convenience, the World Wide Web is the most accessible form of records when mining for information. It is important to note not all statements or descriptions are completely accurate, no matter what form it may be in. Considering this, all records and statistics researched shall be reflected on with a bit of common sense and logic. Conclusions shall be drawn listing advantages and disadvantages, in due course, supplying IPRO 315 with blueprint ideas and concepts.

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Hybrid Drive Train Configurations Parallel vs. Series


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Ryan S. LIM, Sungwoo MIN, Jeongwoo LEE — Hybrid electric electric drive trains have been developed developed recently recently and they are slowly slowly changi changing ng the automo automotiv tive e indust industry. ry. There There are two main categor categories ies of hybrid hybrid drive drive trains trains, , parallel parallel and series series configuratio configurations. ns. They both have have unique advantages advantages and can produce produce nearly nearly the same results. results. This section illustrates the characteristics of the two hybrid hybrid drive train configurations and their feasibilities for the ‘IPRO 315 – Hybrid Electric Bicycle Project’. After carefully examining the two alternatives, the parallel hybrid drive train configuration was selected for the project since it requires less payload space and its complexity would provide the team members wider areas of subjects to learn. Abstract

I. IINTRODUCTION

T has been shown that hybrid electric drive train configurations can greatly reduce the workload of the conventional conventional internal combustion engines, thus improving the fuel effic efficien iency cy and and the emiss emissio ion n chara characte cteri risti stics cs of an autom automobi obile le. . Same Same ideas ideas can can be applied to a bicycle by substituting the cyclist in the place of the hybrid electric vehicle’s vehicle’s internal combustio combustion n engine. In this section, section, the two main main hybrid electric electric drive train configurations, parallel and series configurations will be investigated. It will also include the down-selection of one hybrid electric configuration for the ‘IPRO 315 – Hybrid Electric Bicycle Project’. II. BACKGROUND Even though defining what a hybrid drive train configuration is can lead to endless debat debates, es, ther there e are gener general ally ly two main main categ categori ories es of hybri hybrid d elect electric ric driv drive e train train configur configurati ations, ons, paralle parallel l and series configu configurat rations ions. . A parallel parallel hybrid hybrid electric electric configuration configuration consists of a conventional conventional and a battery-electri battery-electric c drive train (electric motor), which are coupled at the level of the transmission or at the wheels. Vehicles with a parallel hybrid electric drive train are generally able to run either in an ICE (Internal (Internal Combustion Engine) mode, a hybrid mode, or in a pure-electric pure-electric mode with the engine engine switched switched off dependin depending g on the driving driving condit conditions ions. . During During ICE-driv ICE-driving ing the electric electric drive drive train provide provides s the option for regenera regenerative tive braking braking. . During During hybrid hybrid driving, the IC engine engine can also also charge charge the battery. battery. The electric electric mode is is generally generally used for city city driving. driving. This avoids avoids cold start start emissions emissions taking place place in urban urban areas and avoids avoids the use of of the ICE in unfavorable unfavorable areas areas of its engine engine map. map. In rural and and highway highway driving driving the ICE runs nearer nearer to its optimal optimal point point yielding yielding acceptabl acceptable e fuel consumption consumption and emissions. emissions. In a series hybrid electric configuration, configuration, the electric electric motor motor that that drives drives the wheels derives derives its electrici electricity ty from either a battery battery or an engine-generato engine-generator r set or from both simultane simultaneously. ously. The engine-generat engine-generator or set generally generally supplies the average demanded power, while an energy storage device (mostly a battery but also super-capacitors or electromechanical flywheels are applied) supplies peak power. power. Under Under low load conditi conditions ons and during during regener regenerativ ative e braking braking the battery battery is recha recharge rged. d. In general general serie series-h s-hyb ybrid rids s are charg charge e susta sustain ining ing and do not not requ require ire char chargi ging ng from from the the grid grid. . Para Parall llel el and and seri series es hybr hybrid id elec electr tric ic driv drive e trai train n configurations are different ways of achieving nearly the same ends. When compared to a series hybrid, the parallel has some shortcomings because it is more complicated and needs more more computer computer power to manage manage the the energy flow. flow. But the parallel parallel could could be more more efficient on the highway and will not take up as much vehicle space as the series drive train would. Schematic representations of the two hybrid electric drive train configurations are shown in the appendix. 


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III. RESULTS Even though both the parallel and the series hybrid electric drive train can be installed on a bicycle and produce nearly the same results, the parallel configuration was chosen for the ‘IPRO 315 – Hybrid Electric Bicycle Project’ for various reasons. First, a parallel hybrid configuration does not require as much space as a series configur configurati ation on would. would. Since Since all the driving driving power power come from either either a battery battery or a generator in a series configuration, more than one motor or battery might be needed to produce desired power output for a series configuration, thus requiring more payload space. A bicycle is a relatively relatively simple simple structure structure and does does not have have much space space when compared to an automobile, thus minimizing the space requirements for the equipments is very crucia crucial l for the project project. . Also Also there is a major major shortcomi shortcoming ng with a series series configuration. configuration. What if the battery dies? In such such cases, the cyclist would have to pedal to generate electricity but it would be hard to generate enough electricity electricity for opera operatio tion n witho without ut actua actuall lly y chargi charging ng the batter battery. y. Lastl Lastly, y, even even thoug though h paral paralle lel l configuration is more complicated and needs more computer power to manage the energy flow, it was chosen because it would provide team members wider areas of subjects to learn. learn. Keeping Keeping in mind mind the goal of the proje project, ct, that that is to learn and experi experienc ence e innovative innovative ideas, a parallel parallel configuration was determined to be better suited for the project. IV. CONCLUSION After carefully examining the two alternatives, the parallel and series hybrid drive train train, , the paralle parallel l hybri hybrid d drive drive train train was was selec selected ted for the the ‘IPRO ‘IPRO 315 315 – Hybri Hybrid d Electric Bicycle Project’. Less payload space requirement and wider areas of subjects to learn learn that that the paral parallel lel syste system m provi provide des s were were the the key key reaso reasons ns of choos choosing ing the parallel parallel hybrid hybrid drive drive train. The IRPO team team members members will install install a parallel parallel hybrid hybrid drive train on a bike and learn various innovative ideas while building the hybrid electric bicycle. If time and budget permit, a series hybrid drive train will also be installed on a bike and various characteristics of the two drive train alternatives will be compared.

APPENDIX


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Figure 1 – Schematic representation of parallel hybrid electric drive train

Engine

Generator

Controller

Motor

Wheel

Battery Figure 2 – Schematic representation of series hybrid electric drive train

REFERENCES

[1] [2] [3] [4]

"Prius – New Car Features", Features", Toyota Motor Motor Corporation, Corporation, May 2000. "Hybrid Electric Electric Vehicles", http://www.ott http://www.ott.doe.gov/h .doe.gov/hev/ ev/ "Series vs. Parallel: The jury’s still out on tomorrow’s HEVs", http://www.uscar.o http://www.uscar.org/techno/ rg/techno/svsp.htm svsp.htm "Optimal Design of Hybrid Electric-Human Powered Lightweight Transportation", http://www.webs1.uidaho.edu/niatt/research/UTC_projects/year2/klk320.htm [5] "A Student’s Guide to Alternate Fuel Vehicles", Vehicles", http://www.energyquest.ca. http://www.energyquest.ca.gov/transp gov/transportation/ ortation/index.html index.html

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Ryan S. LIM, Sungwoo MIN, Jeongwoo LEE

Chain Drive vs. Shaft Drive Abstract — The development of the chain drive helped make the bicycle that we know today possible. possible. More recently recently, , bicycles bicycles with a shaft drive drive have been been developed developed and it is slowly slowly changing the bike industry. They both have unique advantages and can produce nearly the same efficiency. This section illustrates the characteristics of the two alternate drive mechanisms, chain chain drive drive and shaft shaft drive, drive, and their feasib feasibili ilitie ties s for the ‘IPRO 315 – Hybrid Hybrid Electric Electric Bicycle Project’. After carefully examining the two alternatives, alternatives, the conventional conventional chain drive was selected for the project since its cost and flexibility were determined to be better suited for the project.

I. TINTRODUCTION

HE devel develop opmen ment t of the chain chain drive drive helpe helped d make make the the bicyc bicycle le that that we know know today today possible. possible. The chain drive drive eliminated eliminated the need need to have the the cyclist directly directly above above the wheel. wheel. Instead Instead the cyclist cyclist could could be positioned positioned betwee between n the two wheels for better better balance. More recently, recently, bicycles bicycles with with a shaft shaft drive have have been developed developed and it is slowly slowly changing changing the bike bike industry. industry. In this sectio section, n, both the chain chain drive and the shaft drive will be investigated. It will also include the down-selection of one drive mechanism for the ‘IPRO 315 – Hybrid Electric Bicycle Project’. II. BACKGROUND Leonardo Da Vinci is credited with developing the idea of the chain and cog in the 15th century. [1] However, However, it took nearly 400 years for the idea to become a practical aspect aspect of bicycle bicycle design design. . For a chain chain drive to be effecti effective ve it needs needs to transmit transmit power efficiently efficiently from the rider’s rider’s legs legs to the back back wheel. It also must must be designed designed so that pedal pedalin ing g resis resista tance nce is within within a comfo comforta rtabl ble e range range for the cyclis cyclist. t. The developm development ent of stronger stronger material materials s and other other technol technologic ogical al and engineer engineering ing advances advances made this possible. By the 1880s, the chain drive was commonplace. The The shaf shaft t driv drive e has has been been deve develo lope ped d more more rece recent ntly ly and and only only few few comp compan anie ies s are are manuf manufact actur uring ing those those types. types. The shaft shaft drive drive uses uses a shaft shaft instea instead d of a chain chain to transmit power from the rider’s legs to the wheels. Typically gears are sealed inside a hous housing ing that that are attach attached ed to the main shaft. shaft. The The numbe number r of the shaf shaft t driv drive e manufacturers is increasing and public interests are growing as well. It is slowly changing the bike industry. industry. Pictures Pictures of a typical typical shaft shaft drive and and a typical typical shaft shaft driven bicycle, which are currently being sold in the market, are enclosed in the appendix. A chain or shaft drive alone (without gears) is effective on flat surfaces and going downhill. downhill. However, when when it comes comes to headwinds, headwinds, hill climbing, climbing, and and even starting starting on a bicyc bicycle le with without out gears gears, , the the cyclis cyclist t has has to stand stand on his his pedal pedals s and and strai strain n while while pedaling at at a very low low rate. Gears allow allow the cyclist cyclist to pedal pedal at a comfortable comfortable and and efficien efficient t rate while traveling traveling either uphill uphill or downhill downhill or with a headwind headwind or a tailwind. tailwind. On the old high-wheelers, high-wheelers, the the pedals were were attached attached directly directly to the wheel. wheel. One turn turn of the pedals pedals equaled equaled one turn turn of the wheel. wheel. Gears Gears allow allow the cyclist cyclist to change that that ratio. For steep hills, the cyclist would would choose choose a gear that that turns turns the pedals many times to turn the wheel just once. On flats or downhill’s, the cyclist might choose a gear that turns the wheel many times for each turn of the pedals. III. RESULTS Both the chain drive and the shaft drive have their own advantages and they produce similar performa performance nce efficiencies efficiencies at about 95%. 95%. It seems that shaft shaft drive has has more advantages advantages than than the the chain chain drive. drive. The shaft shaft drive is safer safer and and simple. simple. It eliminates eliminates the danger of of chain slap while while riding riding over terrain. terrain. It is cleaner cleaner and the rider rider does not have to deal deal with the greasy greasy chain anymore. anymore. Also it is more more durable and and requires requires low mainten maintenance ance since since all transmiss transmission ion parts parts are enclosed. enclosed. Even though though the shaft shaft drive seems to be a promising choice for the project, the conventional chain drive was chosen for for the ‘IPRO 315 315 – Hybrid Electric Electric Bicycle Bicycle Project’ Project’ for various various reasons. reasons. The

IPRO 315 – HYBRID ELECTRIC BICYCLE 8 chain drive is more flexible and it can absorb more shocks since it can stretch. Also it has more rooms for various gears and as mentioned in the background part of this report, having various gear ratios is crucial for a smooth comfort ride. In addition, it is cheaper than the shaft drive. With the limited budget for the project, reducing the cost cost was one of the most import importanc ance e facto factors rs in makin making g decis decision ions. s. Anoth Another er important reason for choosing the chain drive was due to the fact that the shaft drive mechanism mechanism typically typically cannot be installed installed on an existing existing normal normal bicycle. In order to use a shaft shaft drive drive, , one woul would d typic typical ally ly have have to buil build d a whole whole bike from from scrat scratch. ch. Keeping in mind that the bicycle for the project would most likely be donated, the chain drive was chosen to be better suited for the project. IV. CONCLUSION After carefully examining the two alternatives, the chain and shaft drive, the chain drive was selected selected for for the ‘IPRO 315 315 – Hybrid Electric Electric Bicycle Bicycle Project’. Project’. Less cost, more flexibility, and easy modifications were the key reasons of choosing the chain drive. drive. The IRPO IRPO team members members will use the existi existing ng chain drive drive on a conventi conventional onal bike. bike. Various Various gear gear ratios ratios will be tested tested under various various biking biking conditi conditions ons and any necessary modifications on the drive mechanism will be made to achieve the optimal efficiency.

APPENDIX

Figure 1 – Example of a typical shaft drive


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Figure 2 – Bicycle with a shaft drive

REFERENCES

[6] [7]

Sigvard Strandh, "Machines, illustrated history", Draeger editor, 1979, pp. 219. "Amis Chainless Shaft Drive Bicycles & Trikke", http://www.chainless.com/ [8] "Zero Shaft drive cycles", http://www.ethicalw http://www.ethicalwebsites.c ebsites.co.uk/zero/ o.uk/zero/faq.php?b faq.php?back=index. ack=index.php php [9] "Bicycle History", http://members.aol. http://members.aol.com/bicyc com/bicyclemus/bike lemus/bike_museum/P _museum/PHbikbio.ht Hbikbio.htm m

Permanent Magnet Motors Waqas Bin JAMAL Abstract- Permanent magnet motors are well fit for use where response time is a factor. Their speed characteristics are similar to those of shunt wound motors. Built with a conventional armature, they use permanent magnets rather than windings in the field section. DC power is supplied only to the armature. Since the field is constant at all times, the performance curve is linear, and current draw varies linearly with torque. They are not expensive to operate since they require no field supply. The magnets, however, loose their magnetic properties over time, and this effects less than rated torque production. Some motors have windings built into the field magnets that re-magnetize the cores and prevent this from happening. DC permanent magnet motors produce high torque at low speed, and are self-braking upon disconnection of electr electrica ical l power. power. Perman Permanent ent magnet magnet motors motors cannot cannot endure endure contin continuou uous s operat operation ion becaus because e they they overheat rapidly, destroying the permanent magnets.

I.INTRODUCTION

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Electronic motion control became popular in industry in the 1970s when machine tool compa companie nies s start started ed conve converti rting ng their their produ products cts from from hydra hydrauli ulic c to elect electric ric contr control. ol. Embedded processors were just becoming practical in commercial applications. Digital control was in its infancy and the controllers of that day were barely able to keep up with the job. In fact, the processors processors were nearly consumed just generating generating the cycleby-cycle by-cycle position position commands commands and monitorin monitoring g the machine machine I/O. For the most part, part, the control loops were closed in analog circuitry. The motor of choice was the permanent magnet (PM) DC brush motor, primarily because those motors are easy to control.

II.BACKGROUND Permanent Magnet Motor Construction

HNICALINFATION The DC brush type are most commonly found in low-end to mid-range mid-range CNC machinery. The “brush” refers to brushes that pass electric current to the rotor of the rotating core of the motor. The construction consists of a magnet stator outside and a coil rotor inside. A brush DC motor has more than one coil. Each coil is angularly displaced from one another so when the torque from one coil has dropped off, current is automatically switched switched to another another coil which which is properl properly y located located to produce produce maximum maximum torque. torque. The switching is accomplished mechanically by the brushes and a commutator as shown below.

All motors generate torque through the interaction of two magnetic forces: the field and the armature. In PM motors, the magnets generate the field so the controlling elect electron ronic ics s (the (the “drive “drive”) ”) need need only only regul regulate ate the the elec electro tro-ma -magn gneti etic c field field in the the armature by regulating armature current. If everything in a motor is lined up right, putting current in the armature makes torque. The problem with electric motors is that once the motor starts to turn, everything isn’t lined up right anymore. After the motor moves, you have to change the current in the armature. Moving the current as the motor rotates is called “commutation.” “commutation.” The reason brush motors are easy to control is that commutation is mechanical. As the motor rotates, brushes slide along a commutator bar connecting in different sets of armature windings at different motor positions.


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III.COMPARISON BETWEEN BRUSHLESS AND BRUSH MOTORS

Brushle Brushless ss motors motors require require more more power power devices devices and more wiring. wiring. Brush-mo Brush-motor tor systems systems enjoy enjoy a cost cost advan advantag tage, e, espe especia ciall lly y in the the lowe lower r power power ratin ratings gs where where the cost cost of control is a larger portion of the system cost. Sometimes brushless motors do not produce torque as smoothly as do brush motors, mainly because the offset error common in current sensors causes torque ripple in brushless brushless motors, but not in brush motors. Still Still, , the the adva advanta ntages ges of brush brushle less ss motor motors s ofte often n win win out out as the cost cost of contr controls ols continues to fall. Table 1 provides a brief comparison of the two motor types.

Advantages of brush motors

Advantages of brushless motors

Simple Drive Electronics. No posi positi tion on sens sensor or requ requir ired ed by driv drive. e. Offset in current sensor does not cause torque ripple. Lower cost, especially in low-power applications.

Reduced maintenance; improved reliability. Elim Elimin inat atio ion n of of arc arcin ing. g. Smaller motor due to easier heat removal and elimination of commutation bar.

Smaller rotor inertia. Elimination of brush noise, brush friction and no carbon debris. Table 1,Comparison between brush and brushless motor

IV.RESULTS


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The simplicity of controlling brush motors is offset by a number of problems, almost all of which which resul result t from from the the brush brushes es. . The The brus brushes hes arc under under heavy heavy curre current nt load, load, sometimes generating severe electrical noise. The brushes wear and must be replaced regularly and are cast of carbon dust. The rotors of brush motors are large for two reasons. First, the rotor is constructed with high-inertia material: copper wire is wound around a steel core. Second, the motor length is extended extended to allow room for the commutator assembly. The result is a heavy rotor, ill designed for moving the light inertias inertias common common in servo servo applica application tions. s. Finally, Finally, because because the winding windings s are rotatin rotating g inside the stator, it’s difficult to remove heat. This usually forces the rotor to be enlarged further to make room for gauge larger wire, which generates less heat.

Applications Robotics and factory automation • Pick-and-place robots • Positioning tables • Welding wire feeders • Automatic guided vehicles • Bar-coding equipment Computer and office equipment • Copier and microfilm machines • Printers / plotters • Tape drives

Industrial equipment • Automatic door actuators • Material handling equipment • Packaging, marking and sorting equipment • Machine tools • Web drives • Gimbal controlled cameras for security systems • Antenna drives Medical equipment • Electric wheelchairs and scooters • Bio-analytical equipment • Medical pumps • Centrifuges Technical Information Table 2 provides some technical specifications of various kinds of Permanent Magnet motors. Type

J (Kg- Performance Power d.c. (A) Nominal Nominal torque (Nm) (Nm) (rpm) Armature Armature (V) (Kw) (%) m2)

3412/24

0,12

1,2

0,48

2400

170

3418/24

0,18

1,6

0,73

2400

170

3425/24

0,25

2,1

1,00

2400

170

0,33-103

0,36-103

0,52-103

FF

Weight (Kg)

60

1,05

3,6

67

1,05

3,8

70

1,05

4,2


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4610/24

0,18

1,5

0,73

2400

170

4622/24

0,25

1,9

1,0

2400

170

4630/24

0,37

2,7

1,5

2400

170

4640/24

0,55

3,8

2,3

2400

170

4660/24

0,75

5,0

3,0

2400

170

4680/24

1,1

7,4

4,5

2400

170

6638/24

1,5

9,8

6,1

2400

170

6657/24

2,2

14,5

8,9

2400

170

6681/24

3

19,8

12,1

2400

170

0,64-103

1,20-103

1,60-103

2,30-103

3,20-103

4,00-103

9,00-103

12,0010-3 16,0-103

70

1,3

7,0

78

1,05

8,0

80

1,05

9,5

85

1,05

11,5

87

1,05

15,0

88

1,05

18,0

89

1,05

23,0

89

1,05

31,0

89

1,05

37,0

Table 2,Technical Specifications

REFERENCES

[10] Amitava Basak, “Permanent Magnet DC Linear Motors,” Oxford University Press, February 1996 [11] Jacek F. Gieras, Mitchell Wing, “Linear “ Linear Synchronous Motors: Transportation and Automation Systems ,” CRC

Press, January 2000 [12] Jacek F. Gieras, Mitchell Wing, “Permanent “ Permanent Magnet Motor Technology: Design and Applications ,” Marcel

Dekker, January 1997 [13]http://www.miprosyn.com/htmluk/magneti.htm


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Brushless DC Motors Leo CARRERA

Abstract - Brushless motors provide less maintenance, long life, low EMI, and quiet operation. They produce more output power per frame size than PM or shunt wound motors and gear motors. Low rotor rotor inerti inertia a improv improves es accele accelerat ration ion and decele decelerat ration ion times times while while shorte shortenin ning g operat operating ing cycles and their linear speed/torque characteristics produce predictable speed regulation. With brushless motors, brush inspection is eliminated making them ideal for limited access areas and applications where servicing is difficult. Low voltage models are ideal for battery operation, portable equipment, or medical applications where shock hazards cannot be tolerated.

V.INTRODUCTION

Brushless Operation Efficiency and Heat Dissipation Rotor Rotor motion motion is started started by generati generating ng a revolvin revolving g magneti magnetic c field field in the stator windings windings, , which which interact interact with permane permanent nt magnet magnet fields fields in the rotor. rotor. The revolvin revolving g 

IPRO 315 – HYBRID ELECTRIC BICYCLE 15 field is created by sequentially energizing the winding phase pairs. The winding phase pairs pairs are energ energize ized d with with curre current nt flow flow in a set seque sequenc nce e to produ produce ce the the desi desired red direction of rotation. At any instant, two of the three phases are energized while the third phase is off. Energizing two phases simultaneously combines the torque output of both phases phases and increases increases overall overall torque output. output. Motor power leads are equipped equipped with quick disconnect terminals or terminal blocks for easy control board connection. A conventional brushless motor has the windings attached to the case and the magnets attached to the rotating part. Brushless motors work by electronically switching the motor current on and off in the different windings so there is no commutator and no brushes brushes to bounce bounce and loose efficie efficiency. ncy. This is why brushless brushless motors need special special controllers. Because the coils are in contact with the case they can get rid of the waste heat bett better er. . This This allo allows ws the the brus brushl hles ess s moto motor r to use use more more powe power r and and run run fast faster er. . The The brushless motor is both more efficient and able to work efficiently over a greater range of cells and currents. The two main sub-divisions of brushless motors refer to how the current through the windings is sensed and controlled. The original motors had small sensors inside to sense the position and movement of the armature and allow the electronics to control the current to the windings. windings. These have typically typically 3 main heavy duty wires which carry the drive current and additionally a set of small wires (often 5 or 6) connected to the internal sensors. They generally work only with specific controllers from the same manufacturer. Advances in electronics now allow the current to be controlled without the need for these sensors, which are relatively fragile and take up space which could otherwise be used for magnets or windings. It is common now to hear that this newer type of motor are are "sen "senso sor r less less". ". This This tech techno nolo logy gy allo allows ws to sele select ct the the cont contro roll ller er and and moto motor r separ separate ately ly agai again. n. There There used used to be a consid consider erabl able e cost cost to this. this. The The sensor sensor less less cont contro roll ller ers s were were VERY VERY expe expens nsiv ive e but but the the late latest st impr improv ovem emen ents ts in soft softwa ware re and and electronics have made them a lot more affordable. Almost all the current production brushless motors are sensorless. In fact a sensor less controller can also be used with a conventional brushless motor (you just don't connect the sensor harness). The latest type of brushless motor available is the so-called so-called "out runner". At first sight these are rather odd. They are arranged the same way round as a brushed motor with the coils in the center and the magnets on the can. But...it is the CAN which rotates NOT the center armature. This means they are a bit tricky to mount since you obviously obviously can't just clamp them down but it does have one BIG advantage. These motors generate much more torque than a conventional arrangement. In practice what this means is that that they they will will turn turn a much much large larger r and more effic efficien ient t load load with without out needin needing g a gear gearbo box. x. Gear Gearbo boxe xes s of cour course se add add comp comple lexi xity ty, , cost cost and and weig weight ht so that that's 's a real real advantage. As far as the motor designations go there are no standards for brushless motors. Each of the manufacturers has their own style. It is needed either to be able to read and understand motor constants or, better yet, to ask the manufacturer/seller when purchasing a motor.

VI.BACKGROUND Brushless Advantages Brushless motors provide less maintenance, long life, low EMI, and quiet operation. They produce more output power per frame size than PM or shunt wound motors and gear moto motors rs. . Low Low roto rotor r iner inerti tia a impr improv oves es acce accele lera rati tion on and and dece decele lera rati tion on time times s whil while e shorteni shortening ng operati operating ng cycles cycles and their their linear linear speed/t speed/torqu orque e charact characteris eristics tics produce produce predictable speed regulation. With brushless motors, brush inspection is eliminated makin making g them them ideal ideal for for limit limited ed acce access ss areas areas and applic applicat ation ions s where where servi servici cing ng is difficult. difficult. Low voltage models are ideal for battery operation, portable equipment, equipment, or medical applications where shock hazards cannot be tolerated.


16

Brushless Construction Often brushless motors have a three-phase four-pole configuration. Internally, the motor features a wound stator (stationary (stationary outer member) and a permanent magnet rotor. Having Having the winding winding in the outer outer member member helps helps dissipat dissipate e winding winding heat efficientl efficiently. y. Stator windings are connected in a conventional three-phase wye configuration. The roto rotor r cons consis ists ts of a shaf shaft t and and a core core with with rare rare eart earth h perm perman anen ent t magn magnet ets s its its circumference providing inherent low inertia Factors Affecting Motor Life The primary failure mode for brushless motors is bearing failure. Temperature is also a factor that limits the life of any motor. Heat is generated in the motor windings and must be dissipated primarily through the motor casing. The motor’s ability to perform is directly related to the difference between ambient temperature temperature and the maximum permissible rotor temperature, temperature, as well as the duty cycle. Winding Winding resista resistance nce rises rises and magnetic magnetic forces forces decreas decrease e as temperat temperature ure rises. rises. This This results in decreased performance. These factors must be considered when operating at high high conti continu nuous ous load loads. s. Meas Measure ures s such such as forc forced ed airair-coo coolin ling g and and heat heat sink sinking ing can can significantly lower motor operating temperatures.

Technical Information

REFERENCES

[14]S. J. Chapman, "Electric Machinery and Power Systems Fundamentals," New York: McGraw Hill 2002. [15] F. Munesh, "Electric Motors," Boston Publishers, 5 th Edition 1976.

[16]Brushless motors operation, Internet Resource


17

[17]AC Motors, Internet Resource.

Planetary Gear Train Ryan S. LIM, Sungwoo MIN, Jeongwoo LEE Abstract — The development of Hybrid Electric Vehicle (HEV) has been needed a new type of gear train for power train rather than conventional gear trains. The new type of gear train is the planetary planetary gear train. In the automobile automobile industry, planetary planetary gear train has been being used in power train between an internal combustion engine and an electric motor. This section describes the principle of planetary gear train and its possibilities of application for the ‘IPRO 315 – Hybrid Electric Bicycle Project’. In order to control

I. TINTRODUCTION

HE conventional gear trains are all one-degree-of-freedom (1-DOF) devices. Another class of gear train, the planetary train, has wide applications. This is a 2-DOF device. Two inputs are needed to obtain a predictable output. In some cases, such as 

IPRO 315 – HYBRID ELECTRIC BICYCLE 18 the automotive differential, one input is provided (the drive shaft) and two frictionally coupled outputs are obtained (the two driving wheels). In this paper, the principle of planetary gear train will be described and the possibilities of application for the ‘IPRO 315 – Hybrid Electric Bicycle Project’ will be discussed.

II. BACKGROUND Planetary gear trains have several advantages over conventional trains, among which are higher train ratios obtainable in smaller packages, reversion by default, and simultaneous, concentric, bi-directional outputs available from a single unidirectional input. These features make planetary trains popular as automatic transmissions in automobiles and trucks, etc. Figure 1, in the Appendix, shows the gear set free to rotate as an arm that connects the two gears. The system DOF of this gear set is 2. This has become a planetary gear train with a sun gear and a planet gear orbiting around the sun, held in orbit by the arm. Two inputs are required. Typically, the arm and the sun gear will each be driven in some direction at some velocities. In this configuration, if a ring gear is added as shown in Figure 1, the planetary gear train becomes more useful. This ring gear meshes with the planet and pivots concentric with the pinion, so it can be easily tapped as the output member. Most planetary trains will be arranged with ring gears to bring the planetary motion back to a grounded pivot.

III. RESULTS In the HEV system, this planetary gear train has been used for power train between an internal combustion engine and an electric motor. The power controller in the HEV could could select select the the gear gear for power power input input from from an inte interna rnal l comb combust ustio ion n engin engine e and and an electric motor. It could be either the ring gear or the arm, and it could both. In a normal bicycle, the conventional power source is pedaling. Thus, in the Hybrid Electric Bicycle, the pedaling by a rider could be the internal combustion engine in the HEV. Similarly, the planetary gear set may control the power from the pedaling and electric motor by either automatically or manually. Howe Howeve ver, r, bicy bicycl cles es have have chai chains ns, , fron front t spro sprock cket et, , and and rear rear gear gear sets sets, , so it is difficult to mount the planetary gear train among them. In addition, in order to use planetary planetary gear train, all those components components should be connected connected together, because both the pedaling and the electric motor have to transmit the power to the planetary gear train. Therefore, the system of Hybrid Electric Bicycle would be more complicated. In Electric Bicycle market, hub motors have been used. The Hub motors are connected to wheels directly and they transmit the power from the motor to the wheel directly. Thus, if we use the hub motor, the configuration configuration of power train would be simpler than using the normal electric motor and planetary gear train.

IV. CONCLUSION After considering the planetary gear train, if we use conventional power electric motor on the bicycle, there are possibilities to apply it for the ‘IPRO 315 – Hybrid Electric Bicycle Project’. However, it could make the power system of the bicycle more complicated than using the hub motor. If we use the hub motor, the planetary gear train is not needed any more, since the hub motor transmits power to wheels directly. Therefore, Therefore, the other type of system to control the power between the pedaling and the electric motor is needed.


19 APPENDIX

Figure 1 – Example of a planetary gear train

IPRO 315 – HYBRID ELECTRIC BICYCLE Figure 2 – Example of the planetary gear train in HEV

20

REFERENCES [18] Robert L. Norton, “Machine Design-An Integrated Approach” 2 nd Ed. Prentice Hall, 200, pp. 703-704. [19] Leone Martellucci, Chiara Boccaletti,Marco Santoro “A Power Train with Planetary Gear System: Advantages

and a Design Approach”, University of Rome I “La Sapienza”, Dresden University of Technology, pp. 119 [20] “Planetary Gear System”, http://www.sdsc.edu/tmf/Examples/Planetary/planetgear.html

Contra sting Hybr id Electri c Bicycles and Electric Bicycle Michael GEORGE, Sam CHOI — This report examines the difference between — Abstract Bicycl Bicycles. es. The differe difference nces s discus discussed sed focuses focuses on the necessary if an an Electric Bicycle Bicycle would be converted to a of Electric Electric and Hybrid Hybrid bicycl bicycles es are discus discussed sed. . Then Then implementing a Hybrid Bicycle are briefly summarized.

Hybrid Electric Bicycles and Electric compone component nt differen differences ces that would would be Hybrid Electric Electric Bicycle. The benefits the benefit benefits s and possibl possible e method methods s of

I. INTR INTROD ODUC UCTI TION ON This This report report will focus the differe differences nces between between an electric electric bicycle bicycle and a hybrid hybrid 

IPRO 315 – HYBRID ELECTRIC BICYCLE 21 electric bicycle. It will emphasize what an electric bicycle is and the benefits from using using one. Then Then it will consid consider er the benefi benefits ts of a Hybrid Electr Electric ic Bicycle Bicycle and and additional features that are required to transform an electric bike into a hybrid. Then Then cons consid ider erat atio ions ns of ener energy gy cons conser erva vati tion on will will be look looked ed at and and see see if that that transfor transformat mation ion is worthwhi worthwhile. le. Ultimate Ultimately, ly, the questio question n we will try to answer answer is whether or not regenerative regenerative braking is an economically feasible technology technology to explore on electric bicycles.

II. BACKGROUND Electric Bicycle (e-bike): How an e-bike e-bike works works is by assistin assisting g your pedaling. pedaling. Electric Electric bikes are everyday everyday bicycles bicycles with a battery battery-pow -powered ered electric electric motor motor attached attached. . Although Although it is capable capable of pushing pushing you along along without without any pedalin pedaling, g, electri electric c bikes bikes perform perform noticea noticeably bly better better augmented by pedaling. The average "couch potato" who normally rides at 10 mph can ride ride at 15-20 15-20 mph mph using using the the same same effor effort. t. He/s He/she’ he’s s expec expected ted range range can vary vary but but distances of 10 miles can be covered with an appropriate battery, with a recharge time of several hours. Power, when activated by a switch on the handlebar (power-on-demand) or in response to your your pedalin pedaling g (ped-ele (ped-elec), c), gives you an immediat immediate, e, nearly nearly silent push. When When you release the switch (or stop pedaling), the motor coasts or "freewheels" - like when you stop pedaling a regular bike. Just like a regular bike, e-bike is rounded out with a gear and brake controls as well as the power on demand knob. Powe Power-o r-onn-dem demand and means means no pedal pedalin ing g requi required red anytim anytime e at any time time. . Altho Although ugh all electric (or "electric-assist") "electric-assist") bikes are designed to work with your pedaling, poweron-demand on-demand allows you to ride the bike without pedaling. Most systems offer a variable speed control, although some are simply on. A "ped-elec" won't deliver motor power unless it senses you are pedaling and it's "power output to pedal pressure" ratio is usually adjustable. When When conside considering ring an E-bike, E-bike, battery battery issue issue is one of the most talked talked about isuue. Rechargeable batteries, usually sealed lead-acid, provide power for the electric drive motors. Charging costs less than 5¢ of electricity from common 110V AC wall outlets. Charging times vary widely due to charger output and battery capacity, but you can expect to recharge in less than 8 hours with most stock chargers and if one is not happy with 8 hours of charging, quick chargers are available. How e-bikes e-bikes perform depends depends on many factors. factors. The most important important factors factors are listed below with the most important at the top. You will notice that battery size and system efficiency rank near the bottom. One thing to mention is that the speed you go makes a big difference in how far you go. 1. Terrain (For example, incline of hills) 2. E-bike speed speed (range (range at 10 mph is 8 times as as far as at 20 mph) 3. Wind Wind conditions conditions (going (going 10 mph against against a 10 mph headwind headwind feels feels like 20 to the bike) 4. Pulling a trailer (which (which is like like pulling pulling another another bicycle) bicycle) 5. Correct tire tire inflation inflation (under-infl (under-inflated ated tires tires slow you down) 6. Battery size (measured (measured in volt-amp-hours) volt-amp-hours) 7. Weight Weight of rider rider and bike bike frame frame 8. Motor/controlle Motor/controller/drive r/drive system efficiency efficiency I’ve explained briefly, what people can expect from an E-bike and how it differs from a regular bicycle. Then, how is Hybrid Electric Bike different from an E-bike?

Hybrid Electric Bike: Hybrid bike is similar to an e-bike because they both assist the rider with a second power power source. source. The hybrid hybrid engine engine is a combinat combination ion of electri electric c motor with with a power source, source, and a means means to recharge recharge that power power source source from energy energy within within the system. system. (Usually momentum) momentum) The major difference difference between between the electric electric bicycle bicycle and the hybrid hybrid is that the hybrid hybrid employs employs this recharg recharging ing to the battery battery through through a regener regenerativ ative e

IPRO 315 – HYBRID ELECTRIC BICYCLE braking system.

22

To explore level of energy a hybrid electric bicycle can utilize from regenerative braking, proper understanding understanding of the energy usage in a riding situation is necessary. necessary. The two largest forces hindering the movement of an in motion bicyclist is air drag and rolling rolling drag. (Air drag drag becomes becomes a much more more significant significant force force to overcome overcome the the faster the rider is moving) Air Drag: Air drag can be calculated from the equation below.

Airdrag



1

Ac * Cd * Da * v2

2 Ac = Frontal Cross-sectional Area Cd = Drag Drag Coeffic Coefficient ient Da = Density of Air v = velocity The Ac for racers is between 0.4 to 0.6m 2 but crouch so the estimate for this calculation will The drag coefficient is commonly taken as: C d The density of air is known to be: D a = 1.226 Velocity is determined by the rider in m/s.

in this application users will rarely be: A c = .7m2 = 0.9 kg/m 3

Rolling Drag: Rolling drag can be calculated from the equation below.

rolldrag



M * g * Crr

M = mass of rider g = acceleration of gravity Crr = coefficient coefficient of of rolling rolling frict friction ion • • •

The acceleration due to gravity is known as: g = 9.8 m/s 2 Different sources give values for C rr but it will be taken as: C rr = 0.007 Mass is determined by the rider in kg.

So the total drag on a bicyclist is the combination of air drag and rolling drag:

Tdrag = airdrag + rolldrag (Friction loss within the bicycle system is also a factor but will no be factored in because of its extremely variant nature.) To find the power needed to operate a bicycle at a certain velocity you use the equation:

Pvel = v * Tdrag Using this equation a rider going 20 MPH with a total combined bicycle and rider weight weight of 190lbs 190lbs would would have to output output 329W to mainta maintain in his/her his/her speed. speed. From this this equation it can be seen that P vel grows exponentially with velocity.


23 III. RESULTS

Now the question comes as to how much energy can be transferred from the moving bike to a battery. battery. This is the necessa necessary ry componen component t to deem an electric electric bike “hybrid “hybrid.” .” Several assumptio assumptions ns are going going to be made when when doing this this next calculati calculation. on. In the braking all the kinetic energy will be stored in the battery, negating any losses through internal friction, friction, power conversion conversion and assuming assuming this braking will not engage the manual brakes, or that air drag and rolling friction are not a major factor in the stopping. stopping. The reason why why such assumptions assumptions are made made is to establish establish an upper bound bound on how much possible energy could be stored in the battery from braking. The equation for kinetic energy is: U k



1

Mv

2

U k

2 = Kinetic Energy

M

= Mass

v

= velocity

Using the same rider going 20MPH, the kinetic energy would be U

k

= 3443 J.

From this point we start to encounter some real problems that begin to indicate the feasibility feasibility of this this system. If the rider rider were to slow slow down in 1 second from from 20MPH, then that that would be 3443W 3443W of energy sent sent to the battery. battery. This is potenti potentially ally large large amount amount of power that that could be recovere recovered. d. But problem problem comes comes from finding finding a battery battery solution that would be capable of absorbing this much power.

IV. CONCLUSION Since there is a significant amount of energy that can potentially be reabsorbed by the battery, further exploration into how that energy can be stored is warranted. The main issue is getting the energy recovered from the braking into the battery. Various batteries have different methods and speeds at which they can absorb power. Usually, Usually, slow slow charge charge rates rates are used used to extend extend the life of the the battery. battery. For this this application batteries would have to be charged as fast as possible without damaging the battery. Fast charge rates can be used to charge some kinds of batteries, but the small small batte batteries ries used in this this applica application tion cannot cannot handl handle e 3443W 3443W. . And if this this fast charging method is used, the battery must be below 85% of its charge or the fast charging can damage the battery. Basical Basically ly charging charging a battery battery is a fairly fairly complic complicated ated process process. . Many charge chargers rs are designed to limit the current when the battery nears its capacity, which adds more circuitry circuitry to the system. system. With this this added complica complication tion of charge charge rates rates some sort sort of ultra-capacitor or secondary fast charging energy storage device would have to be used to conserve the energy from braking quickly and slowly charge the battery with that energy. One nice aspect of this solution is that the ultra-capacitor would be charged from previous braking and would be able to supply the motor after the rider wanted to start back up. There There are also also a number number of alterna alternative tive methods of storing storing mechani mechanical/ cal/elec electri trical cal ener energy gy requ requir ired ed for for prop propel elli ling ng the the hybr hybrid id vehi vehicl cle e that that have have adva advant ntag ages es and and disadvantages. disadvantages. An alternative energy storage device that can be used is the flywheel. flywheel. Flywheel Flywheels, s, also also known known as electrom electromecha echanica nical l batterie batteries, s, store store energy energy in the form of rotational kinetic energy. The amount of energy stored in the flywheel is calculated as follows:

Thus, an increase in rotational speed is far more beneficial than an increase in the

IPRO 315 – HYBRID ELECTRIC BICYCLE 24 amount of inertia of the flywheel. This fact has steered research towards developing an optimum flywheel shape that allows for the greatest rotational rotational speed possible. The isotropic hyperbolic shape is the most efficient design thus far. Flywheel Energy Storage Using HTS Magnetic Bearings Recent advances in the development of very low friction bearings and high-strength fiber composite rotor materials has revived interest in flywheel energy storage (FES). These advances enable efficient diurnal storage with high energy densities. A rotating permanent-magnet bearing assembly can be stably levitated above a stator component composed of high critical temperature -Tc superconductor (HTS) elements, without the need for positio position n sensors sensors and the elabora elaborate te feedback feedback control control systems systems required required for conventional active electromagnetic bearings. Significant advances have been made at Argon Argonne ne in devel develop oping ing very very low frict frictio ion n magne magnetic tic beari bearing ngs s based based on the uniqu unique e levitation characteristics of HTS materials. Major accomplishments include an order of magni magnitud tude e scal scale-u e-up p in HTS HTS magne magneti tic c beari bearing ng size size and demons demonstr trati ation on of frict frictio ion n coefficients (?< 10-6) more than 3 orders of magnitude better than the best commercial bearings. Potential applications for high-Tc superconducting magnetic bearings range from from spac spacecr ecraft aft gyros gyrosco copes pes to rotat rotatin ing g elect electric rical al machi machiner nery y to energ energy y stora storage ge flywheels. Flywheels offer an attractive alternative to batteries in the development of zerozero-emi emiss ssion ion autom automot otive ive power power syste systems ms. . On a large larger r scale, scale, super supercon conduc ducti ting ng beari bearing/ ng/fl flywh ywhee eel l syste systems ms can be used used for elect electri ric c utili utility ty load load level leveling ing and for for diurnal energy storage. A collaborative collaborative effort with Commonwealth Commonwealth Research Corporation is in progress to demonstrate that low loss HTS bearings can be scaled up to sizes of interest for FES applications. This option is great because a flywheel can receive large amounts of current quickly so would be able to store the energy from the braking immediately. But it is somewhat less feasible within space constraints because of the extra motor and weight required for the flywheel. There are some obvious questions that still need to be addressed, including: “What if the rider rider decid decided ed not to brake brake quickl quickly y and slowly slowly brake braked d over time? time?” ” This This complica complicates tes the problem problem because because the longer the rider rider takes takes to brake, brake, the lost of energy due to drag becomes becomes greater. greater. And if more more energy is lost lost due to drag drag then less less of that energy gets put back into the battery. Incidentally, the rider is unconcerned with this loss due to drag because if energy to drag is not lost now, it will be lost when the rider speeds back up. Clearly there is this and many more questions that still need to be answered to determine if a hybrid electric bicycle is economically feasible. The issues addressed in the paper have pointed to a potentially potentially significant significant source of energy that could be reabsorbed reabsorbed by an electric electric bicycle bicycle system and various various means to store store it. Although all all the ramific ramificatio ations ns and potenti potential al has not been fully fully explore explored, d, we believe believe that the poten potentia tial l of this this proj project ect warra warrants nts furth further er invest investig igati ation on, , even even only only to satis satisfy fy academic curiosity.


E

Bike Bike

and and

25

Hybr Hybrid id

Bike Bike

(Con (Contr tras ast) t)

R EFERENCES EFERENCES [21] [22] [23] [24] [25]

http://www.nlectc.org/txtfiles/batteryguide/ba-cont.htm “New Technologies Battery Guide” http://www.kreuzotter.de/english/espeed.htm#pv “Bicycle Speed and Power Calculator” http://www.et.anl.gov/sections/te/research/flywheel.html “Flywheel Energy Storage” http://www.ott.doe.gov/hev/ “Hybrid Electric Vehicles” http://www.mech.uwa.edu.au/courses/ES407/Storage/1998/flywheel.html “Flywheel”




Kitae KIM,

26

George DERRICK


27

Battery Abstract - The battery is an integral part of this project. The objective of this is to find the correct type of battery for a hybrid electric bicycle. The four batteries studied are lead acid, nickel-cadmium, nickel-metal hydride, and Lithium ion. From the factors that have been used as parameters for the battery the lithium ion battery is the best battery for a hybrid electric bicycle because of its small weight and volume, high efficiency, and quick charge.

I. INTR INTROD ODUC UCTI TION ON The battery is an integral part of this project. What we are establishing in this part of the paper is what kind of battery to use to make the bike work. There are four types of batteries that we looked at using to put on a hybrid electric bicycle. The four types types were: were: lead lead acid, acid, nickel-c nickel-cadm admium, ium, nickel-m nickel-meta etal l hydride, hydride, and Lithium Lithium ion battery. After looking at each of the batteries unique properties, the battery that fits the specifications will mount on the hybrid bicycle. II. BACKGROUND The objective of this is to find the correct type of battery for a hybrid electric bicycle. We will be looking looking at the the specific energy, energy, specific specific power, power, weight, weight, power to weight ratio, cycle life, memory cells, and size. These factors will help choose which battery is the best for utilization. The most important of these factors is specific power and weight. If these factors are within what our project needs a decision will be made on the battery type. III. RESULTS The four batteries studied are lead acid, nickel-cadmium, nickel-metal hydride, and Lithium ion. First, look at the specifications of the lead acid battery. This battery is very inexpensive inexpensive and safe to use and already used on electric electric bicycles from many different different bicycle companies companies. . The two big problems problems with with the lead acid acid battery are are that it has a very low specific energy and a short cycle life. This is going to lead to a low efficiency efficiency and a heavier bicycle, bicycle, two things that will not work with the type of bike our IPRO is trying to make. The next battery we will look at is the nickel-cadmium battery system. This battery has a highe higher r speci specific fic energ energy y and and cycle cycle life life then then the menti mentione oned d above above lead lead acid acid battery. However, this battery does have a memory effect which could cause a problem with the hybrid electric electric system. system. This memory memory effect effect will require require that that in order to recharge the battery the battery must be completely completely empty of energy. If the discharge discharge of the battery is not complete, the battery life will continually decrease. Another problem problem is that the battery battery does not deliver deliver enough enough power. power. Additio Additionall nally, y, the most important problem is that it causes the environment to be polluted. These facts make us hesitate to use the nickel-cadmium battery for hybrid electric bicycle. The third battery is the nickel-metal hydride battery. This battery is what industry is using currently in the hybrid electric electric cars Honda, Toyota, and Ford are making. It has a very good battery cycle life and a practical specific energy and power. However, the reason that this battery is not ideal for this concept is because of the low cell efficiency. This can mean the necessity of a larger battery. The The fourt fourth h and and final final batter battery y is the the lithi lithium um batte battery ry. . This This batt battery ery has a large larger r specific energy and power then that of a nickel-cadmium battery. This battery will also be lighter, smaller and no type of memory infraction. The lithium ion battery only negative aspect is that it has a lower life cycle then the nickel-metal nickel-metal hydride. There are only 500 recharges in a lithium ion battery. [1] IV. CONCLUSION From the factors that have been used as parameters for the battery the lithium ion

IPRO 315 – HYBRID ELECTRIC BICYCLE 28 battery is the best battery for a hybrid electric bicycle. With the power and energy and the regenerati regenerative ve strength strength the battery battery has this fulfill fulfills s all the criteria criteria for building a battery that will power a bicycle and rider safely.

APPENDIX 1. Diagram of lithium ion battery

18650 Cell Specifications

Nominal Nomin al Voltage Nominal Capacity Energy Size Weight Energy Density Gravimetric Volumetric

Charge Duration

3.67 V 2.0 Ah 7.34 W-hr Diameter =18mm Length = 65 mm 42 grams 160 Wh/kg 300 Wh/L 2 – 4 h (100%) 1 h (80%)

Operating Specifications Operating Voltage Charge Voltage Cut-off Voltage Temperature Ran ge

4.2 to 3.0 V 4.2 V ± 50 mV 3.0V -20 to 60

Specifications of the 18650 Li-Ion cell Design: 1

In this design, there are three rows with 6 cells in each row.

7.6 cm

[(2*6 + x*6) * (2*3 + x*3) * (6.5*0.9)] = 605 14.8 Solving for x gives, x = 0.4 cm The distance between the cells = 4 mm. Dimensions of the Aluminum Foam:

Length = 2*6+0.4*6 = 14.4 cm Width = 2*3+0.4*3 = 7.2 cm Height = 6.5*0.9 = 5.85 cm (PCM covers 90% height of the Li-ion cell)


29

Dimensions of the battery box:

Length = 14.4 + 0.4 = 14.8 cm Width = 7.2 + 0.4 = 7.6 cm Height = 6.5 + 1.0 = 7.5 cm (Considering the space occupied by safety circuits) Design: 2

In this design, there are two rows with 9 cells each. [(2*9 + x*9) * (2*2 + x*2) * (6.5*0.9)] = 605 Solving for x gives, x = 0.4 cm The distance between the cells = 4 mm. Dimensions of the Aluminum Foam:

Length = 2*9+0.4*9 = 21.6 cm Width = 2*2+0.4*2 = 4.8 cm Height = 6.5*0.9 = 5.85 cm (PCM covers 90% height of the Li-ion cell) Dimensions of the battery box:

Length = 21.6 + 0.4 = 22.0 cm Width = 4.8 + 0.4 = 5.2 cm Height = 6.5 + 1.0 = 7.5 cm (Considering the space occupied by safety circuits)

22.2

REFERENCES [26] Menahem Anderman, Fritz R. Kalhammer and Donald MaxArthour, " Advanced Batteries for Electric Vehicles:

An Assessment of Performance, Cost, and Availability ", 2000, p 37, p 56. [27] "Batteries", http://www.ott.doe.gov/hev/batteries.html


30

Axial Flux Variable Gap Motor Shaun J. DIGGS

I. IINTRODUCTION

n the field of the electric hybrid vehicles vehicles different types of techniques are used to improve the the life span and efficiency efficiency of the electric electric hybrid hybrid motors. motors. One may achieve achieve better efficiency efficiency by developing developing better ways to convert more of the potential electric

IPRO 315 – HYBRID ELECTRIC BICYCLE 31 energy energy from the rotor-s rotor-stato tator r combinati combination on to kinetic kinetic energy. energy. One way to do this is changing the magnetic flux created by the rotor-stator combination. Dr. Sung Chul Oh and his assoc associat iates es think think they they have have found found that that way throu through gh varia variable ble air air gapp gapping ing. . Although, Dr. Sung’s study may never be used on something as small as the electric hybrid bicycle, we the students of IPRO 315 (The Electric Hybrid Bicycle IPRO) have taken this research into great consideration for the future of hybrid vehicles as a whole. Dr. Sung’s research is as follows:

VII.BACKGROUND Professor Sung Chul Oh and his associates from Granger Power Electronics and Motor Drives Laboratory are testing the application of Axial Flux Variable Gap Motors at Argo Argonn nne e Nati Nation onal al Labo Labora rato tory ry. . This This alte altern rnat ativ ive e elec electr tric ic moto motor r geom geomet etry ry with with potentia potentially lly increase increased d efficie efficiency ncy is being being consider considered ed for hybrid hybrid electric electric vehicle vehicle applications. applications. An axial flux flux motor with with a dynamically dynamically adjustable adjustable air gap gap (requiring (requiring mechanical field weakening) has been tested, analyzed and modeled for use in a vehicle simulation simulation application at Argonne. In essence, changing changing the air gap between rotor and stator changes the magnetic flux. One of the main advantages of adjusting the flux is that that the moto motor r torqu torque e speed speed charac characte teris risti tics cs can be adjus adjusted ted to bette better r match match the the vehicle’ vehicle’s s load. Dr. Sung explains explains that that the challenge challenge in implement implementing ing an electric electric machine with these qualities is to develop a control strategy that takes advantage of the available efficiency improvements without using excessive energy to mechanically adjust the air gap and thus reduce the potential energy savings. The team uses speed, torque, supply supply voltage, voltage, and rotor-to-sta rotor-to-stator tor air gap to map map the motor’s motor’s efficiency. efficiency. A motor motor model model and contr control ol strat strategy egy was was devel develop oped ed using using maps maps of optim optimal al gap gap versu versus s efficiency. efficiency. Dr. Sung claims that he and his his team have improved improved the efficiency efficiency of their tested electric hybrid motor by as much as 3%. The motor model and control strategy was then incorporated into the PSAT (PNGV Systems Analysis Toolkit) vehicle modeling modeling softwa software. re. The variabl variable e air gap control control strategy strategy is being being tested tested in the normal vehicle environment without implementing motor in vehicle by using concept of HIL (hardware (hardware in the loop). loop). PSAT calculates calculates the vehicle’s vehicle’s performance performance in HIL and and the output of the simulator is used as an input command to the dynamo that simulates vehic vehicle le perfo performa rmanc nce. e. The The vehic vehicle le contr control oller ler, , based based on measu measured red vehicle vehicle speed speed deter determin mines es the moto motor r torqu torque e comman command. d. Drivi Driving ng cycles cycles and motor motor perfor performa mance nce in different power train configurations can also be tested using these methods. VIII.C ONCLUSION Although the air gap experiments are still ongoing, Dr. Sung and his team National Laboratory are still make great strides to improve the electric the hybri hybrid d motor motor. . The The futur future e of hybrid hybrid vehicle vehicles s great greatly ly depend depends s on research and design like that of the variable air gap. We of IPRO 315 look the Dr. Sung’s finished product in the mere future. REFERENCES [28]Copyright: 2002-2003, Dr. Sung’s Presentation and Abstract

at Argonne efficiency innova innovativ tive e forward to

Hybrid Electric Bike Research

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