E-Wheel™ - The New Generation of Pedal Electric Cycles (Pedelecs): An Integrated Electric Wheel based on all-in-one idea

Nguyen, Phuoc

E-Wheel™ - The New Generation of Pedal Electric Cycles (Pedelecs): An Integrated Electric Wheel based on all-in-one idea

Summary

This application offers an introduction to the new generation of pedal electric cycles (pedelecs) and ist potential for society in the design and technology in terms of industrial design and mechanical engineering. E-Wheel™, a multi-award-winning patented design, stands for Integrated Electric Wheel, based on all-in-one idea. E-Wheel™ is not just a redesigning of common pedelecs, however, E-Wheel™ and the others will be playing on ever more significant role in our everyday mobility with very positive “support effect” for urban transportation.
Detail CAD data and Finite Element Analysis (FEA) model for both electromechanical and structure analysis are presented in this work and those show that the E-Wheel™ will be take advantage of conventional electric bicycles (e-bikes) or common pedelecs. Besides, the apply-oriented of brushless motor microcontroller design is also presented. The electrical requirements of the controller (voltage, current, frequency) influence the section of components is fully developed and used to illustrate these methods.

Excerpt

Achievements

At the beginning of the project, E-WheelTM has won two prestigious prizes, PR package and

sponsorship:

October, 2013: 3

prize of ASEANpreneurs Autodesk Design Challenge, organized by NUS

Entrepreneurship Society and Autodesk Inc. with the first concept of E-WheelTM. [16]

January, 2014: one of twelve award winners of worldwide Lexus Design Award 2014,

organized by Lexus International, co-hosted by Designboom magazine and DESIGN

ASSOCIATION NPO, with panel display in the Lexus Design Amazing 2014 at the Milan

Design Week 2014 from April 8

to April 13

, 2014. [14]

July, 2014: Two months license of JMAG® software package was sponsored by JSOL Corpora-

tion, Japan for 3D advanced electromechanical analysis.

September, 2014: E-WheelTM was chose to PR for Autodesk Student Experts Marketing

Assets Autodesk Education Expert program, by Autodesk Inc. USA.

Table of Contents

Abstract ... 5

Copyright and Trademark ... 6

Testimonials ... 7

Achievements ... 8

List of Figures ... 11

List of Tables ... 13

Acknowledgments ... 14

Introduction ... 17

1.1

What is a Pedelec? ... 17

1.2

Electricity Consumed by a Pedelec ... 19

1.3

Why E-WheelTM? ... 20

Brushless Direct-Current (BLDC) Motor Design and Optimization ... 22

2.1

Design Strategy and Goals ... 22

2.2

Construction and Operating Principle ... 22

2.3

Motor Constant Prediction Methods: Apply Lorentz Force and Faraday Law

Method ... 29

2.4

Resistance, Losses and Power Rating... 33

2.5

Motor Prototyping Methods ... 38

2.5.1

CAD Modeling ... 38

2.5.2

Fractional Pitch Magnets ... 40

2.6

BLDC Model Analysis and Optimization ... 42

2.6.1

2D Finite Element Method Magnetics ... 45

2.6.2

3D Advanced FEA using JMAG® Designer v13.1 ... 46

Mechanical Design and Prototyping ... 48

3.1

Design Strategy and Goals ... 48

3.2

Design Constraints and Overall Structures ... 48

3.2.1

Design Constraints ... 48

3.2.2

Overall Structures ... 51

3.3

BLDC Motor Skeleton ... 52

3.4

Battery Packs ... 54

3.5

Hub ... 57

3.6

Axle ... 63

3.7

Bearing ... 64

BLDC Motor Controller Design ... 66

4.1

Design Strategy and Goals ... 66

4.2

Controller Design ... 66

4.2.1

Three phase inverter MOSFETs ... 68

4.2.2

Bus Capacitor ... 71

4.2.3

Gate Driver ... 72

4.2.4

Motor Controller ... 74

4.2.5

Position and speed sensing ... 75

4.2.6

Power Supply ... 77

4.2.7

Battery Management ... 77

Conclusions ... 79

References ... 80

Appendices ... 83

List of Figures

Figure 1: General pedelec structure (Figure Courtesy of OXYGEN Bicycles, United

Kingdom) ... 17

Figure 2:

E-WheelTM complete assembly (commercial rendering image) ... 21

Figure 3:

Simplified BLDC Motor Diagram [28] ... 24

Figure 4: Ideal sinusoidal vs. trapezoidal back EMF waveforms, normalized to

RMS=1... 25

Figure 5: BLDC Motor Cross-Section (Source: Redrawn from material furnished by

MICROCHIP Brushless DC (BLDC) Motor Fundamentals) [27] ... 26

Figure 6:

Magnetic flux generated by the small coil of wire passing though the

magnet (from worldwide web) ... 27

Figure 7: Six-Step Commutation (Figure Courtesy of MICROCHIP Brushless DC

(BLDC) Motor Fundamentals) [27] ... 28

Figure 8: (a) A single length of wire in uniform magnetic field (b) A more realistic

depiction of the same interaction in a slotted motor ... 30

Figure 9: A coil of wire moving through a magnetic field that flip direction will

generate a back EMF ... 32

Figure 10: An example of Parameters feature on Autodesk Inventor® Professional ... 39

Figure 11: An example sketch on Autodesk Inventor® Sketch environment with fully

parametric. ... 39

Figure 12: The special BLDC Motor design (view section 3.3) of E-WheelTM (rendering

image) ... 40

Figure 13: BLDC motor having fractional pitch magnets and fractional slot ... 41

Figure 14: Stator winding scheme ... 43

Figure 15: Circuit graph ... 44

Figure 16: The flux distribution in the slotted of BLDC motor with the test current of

7.31 A ... 45

Figure 17: Three-phase 3D Finite Element simulation of the BLDC motor partial model

Magnetic flux density ... 46

Figure 18: Joule losses graph ... 47

Figure 19: Measure over-locknut with calipers ... 49

Figure 20: Disc brake fit info (Source: Redrawn from material furnished by SRAM

Avid disc brake fit info) ... 49

Figure 21: Adjustable-cone freehub ... 50

Figure 22: Ringlè Freehub ... 50

Figure 23: Parts identification of a quick-release mechanism ... 51

Figure 24: 10 mm thru axle (Figure Courtesy of American Classic) ... 51

Figure 25: An exploded view of the E-WheelTM with the special BLDC Motor design

(rendering image) ... 52

Figure 26: BLDC Motor skeleton... 53

Figure 27: Precision pivot lock bolt drawing (Figure Courtesy of MISUMI USA) ... 54

Figure 28: Lithium-ion battery cells arrangement in the battery pack ... 55

Figure 29: The design of the hub with 32 spoke holes (iso left view) ... 58

Figure 30: The cross-sectional of the E-WheelTM ... 59

Figure 31: Loading calculation hierarchical relationships ... 60

Figure 32: Forces applied to the E-WheelTM ... 63

Figure 33: Speed and current control loop configurations for a BLDC motor ... 67

Figure 34: Electrical waveforms in the two phase ON operation and torque ripple ... 68

Figure 35: A typical set of power MOSFET I-V curve ... 69

Figure 36: The bus capacitor is placed across the DC lines, adjacent to the inverter

MOSFET (Three phase inverter) ... 70

Figure 37: DRV8301 Simplified Application Schematic ... 73

Figure 38: Overall block diagram of Hall sensors and BLDC motor microcontroller ... 76

Figure 39: Block diagram of circuitry in a typical Lithium-ion battery pack ... 78

List of Tables

Table 1: The different between kind of electric bicycles (Source: PRESTO Promoting

Electric Cycling for Everyone as a Daily Transport Mode) [8] ... 18

Table 2: BLDC motor design parameters ... 29

Table 3: Parameters used in Rough Analysis of BLDC motor ... 33

Table 4: Calculation of the Resistance for BLDC Motor ... 34

Table 5: Types of Surface Insulation Resistance and Typical Applications (Source:

Selection of Electrical Steels for Magnetic Cores AK Steel) [32] ... 36

Table 6: Total heat capacity calculation for this case... 37

Table 7: BLDC Motor Designed Parameters ... 40

Table 8: Winding parameters ... 42

Table 9: Bill of Materials of BLDC Motor ... 44

Table 10: Performance Comparison between the Rough Calculation and 3D Analysis (at

250 rpm) ... 47

Table 11: Specifications of Panasonic NCR18650 cells (Source: Panasonic battery cells

technical catalogue) [9] ... 55

Table 12: Physical properties of comparison Acetal polymer materials [17] ... 56

Table 13: Key dimensions of the hub ... 62

Table 14: Some specifications for the IR MOSFET IRFS3006PbF ... 69

Table 15: Current flow during the PWM on and off times, assuming the power supply

provides only a DC average current (high power supply inductance and/or

high frequency) ... 71

Table 16: Some Specifications of DRV8301 ... 73

Table 17: TMS320F28027 PiccoloTM microcontroller simplified specifications [24] ... 75

Table 18: Estimating Financial Expenditures, Suppliers and Part/Service Lists for

Prototyping ... 83

Acknowledgments

After exceeding two years and a half on this project, the author would like to express

sincerest thanks and appreciation to many individuals, companies, etc. who have contribut-

ed to this project.

First of all, the author would like to express special appreciation and thanks to M.Eng Le

Khanh Dien for supervising and providing technical support for this study. Very few advisors

would be willing to give as much freedom and trust to explore a new design as he does.

The author would like to thank JSOL Corporation, Japan for providing opportunities to do

interesting hand-on JMAG® software package. In particular, thanks to Mr. Bui Le Hung at

New System Vietnam Co. Ltd., the BLDC Motor electromechanical analysis would not have

been possible without his support. And also, thanks to JSOL staff for corrected BLDC Motor

partial model.

The author would like to express deep gratitude to the advice and assistance from good

friends, colleagues. Among these are Ho Nhat Hung, Ngo Xuan Nghiem, To Dien Son, Dang

Thi Bich Ngoc, Ly Thanh Long, Le Hoang Phong from Ho Chi Minh City University of Technol-

ogy, Dao Doc Truong, Quach Dinh Bao, Tran Le Ngoc Linh from Ho Chi Minh City University

of Science, Dinh Nho Ngoc Lam, FPT-Arena Multimedia, Mr. Vu Viet Hung from John von

Neumann Institute VNUHCM, Ms. Phan Thi Ngoc Mai from Vital System Technology Pte.

Ltd. (Vietnam RO), and my roommate Mr. Phan Tan Hoa.

For the proofreading of certain chapters in this study report, the author would like to thank

Nguyen Hoang Tri from Ho Chi Minh City University of Technology and Education. Thank you

for your many long hours of dedicated work.

Appreciation is also expressed to Mr. Bjørn Wittenberg, Program Manager, Autodesk Inc.

USA. for using this design project to PR for Autodesk Student Experts Marketing Assets 

Autodesk Student Expert program.

The author would like to express appreciation to the representatives from Polaris Laser

Laminations, LLC (USA); Solid Concepts Inc. (USA); Proto Laminations Inc. (USA); Gilbert

Curry Industrial Plastics Co. Ltd. (UK); Hiep Luc Co. Ltd (Vietnam)... In particular, thanks to

Mr. Steve Sprague (Sale Manager of Proto Laminations Inc.) for his kindly providing and

searching for sponsorships.

Thanks are also extended to Mrs. Birgit Lohmann, Lexus Design Award Judge/Designboom

Magazine CEO/Chief Editor; Ms. Danielle Demetriou, British journalist; Mr. Robert Duenner,

Senior Vice President, Wealth Advisor at Morgan Stanley; Mr. Roland Schneider, Mechanical

R&D Engineer, Continental Automotive GmbH; Ms. Nanette Wong, Design Milk Magazine

writer for glowing testimonials, which contributed important improvements.

Gratitude is extended to Ms. Maki Kurihara and Mr. Manabu Kudo at Lexus Design Award

Secretariat Office (Tokyo, Japan), who offered kindly support with highly responsibility

regarding to Milan Design Event.

Thanks to the team at publisher Diplomica Verlag GmbH for your hard work and support to

turning this study report to tremendous community.

Finally, special recognition goes out to my family, for their understanding, support, encour-

agement and patience during my pursuit of this design study. To my farther, my mother and

my younger brother, thank all three of you for your patience and love you more than you

will ever know.

Introduction

1.1

What is a Pedelec?

A pedelec (pedal electric cycle pedelec or electrically power assisted bicycle ePAS) is a

bike with an electric motor, which supplies power assist only when riders pedal. A sensor

(rotation/torque sensor and Hall Effect sensors) measures whether you are pedaling, and

passes this information to a controller. This sensor ensures that the motor only provides

assistance when the rider is pedaling.

Power is delivered by a battery pack, which can be re-charged through a suitable charger

from electric network. Batteries are often mounted to the rack or onto the frame, and

sometimes they are built into the frame.

Figure 1: General pedelec structure (Figure Courtesy of OXYGEN Bicycles, United Kingdom)

The German inventor Egon Gelhard invented and patented the pedelec principle in 1982.

Unfortunately he could not find a cycle manufacturer willingly implementing his ideas in a

product. To be fair, at that time this would have been extremely difficult, because digital motor

control and sensor technology were still in the early stages of development, and could not have

been manufactured at an acceptable price. So it took another ten years until the Japanese

motorbike maker Yamaha developed the first pedelec, and launched it into the Japanese market

in 1993. Yamaha understood that with the pedelec they were dealing with a new category of

vehicle which only intuitively had anything in common with bikes and motorbikes. [7]

Because of the assistance from motor, riding a pedelec makes users feel that there is wind

behind themselves, even when going uphill or in adverse weather conditions. As a result,

you never really sweat nor do you get out of breath. Riding a pedelec has a positive influence

on your physical condition. You can also choose to ride your pedelec without the help of the

electric motor, just as a conventional bicycle.

The advantages go beyond the personal level too, and are relevant to wider society. Accord-

ing to the World Health Organization, 30 minutes of gentle physical exercise are sufficient to

extend life by around 8 years

. Pedelec riding can supply this exercise easily. Thus the

individual is spared illness, and society is spared costs, through reduced sickness days and

increased productivity.

(BICYCLE) PEDELEC

(MOPED) PEDELEC

E-BIKE

Motor only works when

pedalling

Motor only works when

pedalling

Motor always works

Motor stops at

and

motor output is

Motor works above

and motor output

further

obligation

Age limit, helmet, driving

license and insurance

obligations depending on

your country

Age limit, helmet, driving

license and insurance

obligations depending on

your country

Riders can ride on cycle

paths and cycle lanes

In most countries riders are

not allowed to ride on cycle

paths and cycle lanes

In most countries riders are

not allowed to ride on cycle

paths and cycle lanes

Table 1: The different between kind of electric bicycles (Source: PRESTO Promoting Electric Cycling for

Everyone as a Daily Transport Mode) [8]

Even if no renewable energy is used to charge the pedelec the environmental impact of

using a pedelec is probably more positive. This is the case when using a pedelec instead of a

Source: Dr. Günter Klein, WHO-EHEH Bonn. European Centre for the Environment and Health of the WHO.

Presentation: "Wirtschaftliche und menschliche Nutzung körperliche Aktivität im Alltag", 18. 04. 2005.

Conference: Wirtschaft in Bewegung.

car with a combustion engine fuelled with fossil fuels. The positive impact is due to the high

efficiency of the electric motor (80%) in comparison with the low efficiency (25-35%) of the

combustion engine.

1.2

Electricity Consumed by a Pedelec

The question now is what influences the annual electricity consumption of a pedelec? The

amount of power drawn from the battery during one kilometer of cycling depends on a

bunch of factors: [7]

The chosen 'assistance factor' which is usually adjustable by the user. The more assis-

tance is requested from the motor the more electricity will be used. Since control sys-

tems are programmed to assist the human pedalling the electricity used during a cer-

tain time span depends on the intensity of the rider's pedalling. To be exact, it relies

on forces which the rider exerts onto the pedals (ExtraEnergy e. V.). In the extreme of

no electric assistance, for instance in case of an empty battery, no electricity is used

and the pedelec temporarily mutates to a conventional bicycle. The other case is a

very high assistance factor reducing the necessity for pedalling to a very low amount.

In the extreme of the electric assistance replacing completely the human force pedal-

ling would be no longer necessary (however this would then by definition not be a

pedelec but an e-bike in its 'electricity only mode' or an electric scooter).

Slope: In terms of cycling uphill, the steeper the slope is the more electricity on the aver-

age drawn from the battery going increase because the electrical assistance will be high-

er on the average. Otherwise, someone cycling downhill will need little or even no elec-

tric support. In Engel [2008] at

, for a conventional cycle and a flat terrain

are required and, to keep the same speed on a slope of

are needed.

Speed of the vehicle.

Wind speed and direction: head wind (opposite the driving direction) increases the

aerodynamic resistance, hence leading to a higher electricity demand. In contrast,

wind may also drive you from behind (tail wind) and thus reduce the energy con-

sumption.

Mechanical and electric efficiencies of the involved equipment (motor, gear, ergonomic

height of the saddle, etc.). Most relevant of all above components are the air pressure in

the tires as many cyclists will confirm from their own experience. Low efficiencies lead to

an increased electricity demand for the same electro-mechanical assistance.

The number of stop-and-go cycles and of accelerations.

Further parameters as specified in ExtraEnergy e. V. are the position of the rider during

riding and the weight of the ensemble rider and pedelec, e. g. Engel [2008] assumes an

increase

on power for a rise of

on weight on a flat terrain at

and of

for the same weight difference on a slope of

inclination at

1.3

Why E-WheelTM?

For many, at first glance the pedelec is simply a bicycle with some additional electrics. For the

cycle industry, the design opportunities are first limited by the reference to the fundamental

"bicycle" concept, and second by the technical options available for production. However, the

author feels that the pedelec is much more than that, at least, from the viewpoint of a Designer.

It is not only a form of transportation but also it is an expression of the status and lifestyle of

their owners. The task of a Designer for a product which already exists is to make them better

more functional, more beautiful and more practical. Therefore, why it is built like a conventional

bike but with a motor? Why we do not shift to a new level!

This is the main inspiration for the first pedelec concept for nearly two years and a half, it is

called E-WheelTM (abbreviation of Integrated Electric Wheel) An integrated electric wheel

based on all-in-one idea. With the new cutting edge of design pedal electric cycle (pedelec)

E-WheelTM will give the rider new experiments when pedalling. The designs of E-WheelTM are

integrated all of the mechanical and electrical components in a hub very elegantly and be

fitted as a kit to almost any conceivable bike. The core objective remained unchanged.

E-WheelTM are suitable for a wide variety of people who are not able or willingly ride a

conventional bicycle or who simply need faster transportation and most efficient means of

transport in town.

Figure 2: E-WheelTM complete assembly (commercial rendering image)

E-WheelTM is not only eco-friendly but also very lightweight. It is integrated all-in-one:

include 250W (rated power) electric motor, 36V 8.9Ah 320Wh Lithium-ion battery,

electrics drive. E-WheelTM can run up to 60km on one fully charged

and the maximum speed

is 25 km/h. E-WheelTM has the wireless technology for remote control and battery charge.

You can control E-WheelTM by your mobile phone (or control console).

Copenhagen Wheel (superpedestrian.com) [10] is the first success design of retro-fitting

pedelec, since their initial announcement in 2009. But the drive is not the main focus, rather

the gathering of sensor data on air quality and networking to data centers and other users.

With some initial successes, the author would like to inspire the communities to rethink their

attitudes to mobility in a visually dazzling way. At this point, some familiar designs were an-

nounced, for example: FlyKly Smart Wheel [11], Zehus BIKE+ [12], and Electron Wheel [13], etc. The

author sure that many talented designers will push it as far as possible. However, the E-WheelTM

still have unique features which are used in a unique way in the context of overall design.

Maximum range based on one battery full charge, using 150% assistance mode, according to use in ideal

conditions. Distance will vary depending on road conditions, riding surface, cyclist's weight and required

assistance.

Brushless Direct-Current (BLDC) Motor Design and Optimization

2.1

Design Strategy and Goals

The ability to design motors to fit specific applications is an opportunity that is, from the

point of view of author, highly valuable and yet also not well-known. To most, the process of

designing electric motor-based systems involves digging through catalogs of motors, imme-

diately limiting the design space to a set of existing components. By the time this set is

filtered by physical constraints and performance requirements. Breaking down the black-box

status of electric motors to open up new design options is the primary goal of this study.

There is also a significant learning opportunity in designing a `fit-for-purpose' motor, which

may have played an even larger role in the author's motivation to pursue such projects.

Useful analysis techniques include combined CAD/FEA using solid modeling and finite

element magnetic simulation will be clarified.

In summary, the goals of this design study are to:

Evaluate the conditions under which a custom motor design may be called for.

Demystify the design of custom brushless motors by showing simple to advance anal-

ysis and simulation techniques as applied to the case studies.

Provide, though this design, some examples of modern rapid prototyping techniques

for making custom motors.

This chapter approaches the simplest methods, only requiring high school physic skills to

design the BLDC motor.

2.2

Construction and Operating Principle

BLDC motors are a type of synchronous motor. This mean that the magnetic field generated

by the stator and the magnetic field generated by the rotor rotate at the same frequency.

Compare with the induction motors, BLDC motors do not "slip".

BLDC motors come in single-phase, 2-phase and 3-phase configurations. Corresponding to its

type, the stator has the same number of windings. This application only focuses on 3-phase

outer motors.

Stator:

The stator of a BLDC motor consists of stacked steel laminations with windings placed in the

axial slots distribute along the inner periphery. Most BLDC motors have three stator wind-

ings connected in star configuration. Each of these windings are constructed with numerous

coils interconnected to form a winding. One or more coils are placed in the slots and they

are interconnected to make a winding. Each of these windings are distributed over stator

periphery to form an even numbers of poles.

Rotor:

The rotor is made of permanent magnets and can vary from two to many pole pairs with

alternate North (N) and South (S) poles. Based on the required magnetic field density in the

rotor, the proper magnetic materials are chosen to make the rotor. Ferrite magnets are

traditionally used to make permanent magnets. As the technology advances, rare earth alloy

magnets are gaining popularity. The ferrite magnets are less expensive but they have the

disadvantage of low flux density for a given volume. In contrast, the alloy material has high

magnetic density per volume, thus enabling the rotor to compress further for the same

torque. Also, these alloy magnets improve the size-to-weight ratio and give higher torque for

the same size motor using ferrite magnets.

Neodymium (Nd), Samarium Cobalt (SmCo) and the alloy of Neodymium, Ferrite and Boron

(NdFeB) are some examples of rare earth magnets. Continuous research is ongoing to

improve the flux density to compress the rotor further.

Figure 3: Simplified BLDC Motor Diagram [28]

What is back EMF?

When a BLDC motor rotates, each winding generates a voltage known as back Electromotive

Force (or back EMF), which opposes the main voltage supplied to the windings according to

Lenz's Law. The polarity of this back EMF is an opposite direction of the energized voltage.

Back EMF depends mainly on three factors:

Angular velocity of the rotor

Magnetic field generated by rotor magnets

The number of turns in the stator windings

Where

is the number of winding turns per phase, is the length of the rotor, is the

internal radius of the rotor, is the rotor magnetic field density and is the motor's angular

velocity.

Once the motor is designed, the rotor magnetic field and the number of turns in the stator

windings remain constant. The only factor that governs back EMF is the angular velocity or

speed of the rotor and as the speed increases, back EMF also increases.

Details

Pages
Type of Edition: Erstausgabe
Year: 2015
ISBN (PDF): 9783954899579
ISBN (Softcover): 9783954894574
File size: 3.2 MB
Language: English
Publication date: 2017 (May)
Keywords: Pedelec E-Wheel Integrated Electric Wheel All-in-one BLDC Motor

Author

Phuoc Nguyen (Author)

E-Wheel™ - The New Generation of Pedal Electric Cycles (Pedelecs): An Integrated Electric Wheel based on all-in-one idea

Summary

Excerpt

Table Of Contents

Details

Author

Phuoc Nguyen (Author)