See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/287490830
The Design and Construction of an Electric Bicycle. Thesis· April 2015 DOI: 10.13140/RG.2.1.3999.4968
READS
986
1 author:
Olakunle Alao Covenant University Ota Ogun State, Nigeria 4 PUBLICATIONS 0 CITATIONS
SEE PROFILE
All in-text references underlined in blue are linked to publications on ResearchGate,
Available from: Olakunle Alao
letting you access and read them immediately.
Retrieved on: 21 August 2016
THE DESIGN AND CONSTRUCTION OF AN ELECTRIC BICYCLE BY ALAO OLAKUNLE OLUWATOSIN 10CK011233
A PROJECT SUMITTED TO THE DEPARTMENT OF ELECTRICAL AND INFORMATION ENGINEERING, COLLEGE OF ENGINEERING
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A BACHELOR OF ENGINEERING DEGREE IN ELECTRICAL AND ELECTRONICS ENGINEERING
SUPERVISOR: PROF. AWOSOPE C.O.A APRIL, 2015
DECLARATION I hereby declare that the work reported in this project was carried out in the Department of Electrical and Information Engineering, Covenant University, under the supervision of Prof. C.O.A Awosope. I also solemnly declare that to the best of my knowledge, no part of this report has been submitted here or elsewhere in a previous application for the award of a degree. All sources of knowledge used have been duly acknowledged.
………………………………………………………………. ALAO OLAKUNLE OLUWATOSIN (10CK011233)
CERTIFICATION
This is to certify that the Project titled “Design and Construction of an Electric Bicycle” by Alao Olakunle Oluwatosin, meets the requirements and regulations governing the award of the Bachelor of engineering, B.Eng. (Electrical and Electronics Engineering) degree of Covenant University and is approved for its contribution to knowledge and literary presentation.
Supervisor:
Sign: ……………………… Name: Prof C.O.A Awosope
Internal Examiner:
Sign: ……………………… Name:
Head of Department:
Sign: ……………………… Name: Dr F.E Idachaba
External Examiner:
Sign: ……………………… Name:
………….…….. Date
………….…….. Date
………….…….. Date
………….…….. Date
DEDICATION This work is dedicated firstly to God Almighty, the first and greatest engineer ever; my Parents who, through their immeasurable love and care, have afforded me with the opportunity in making this project a reality. They have really been a pillar of support in my life and may God bless them abundantly, amen.
ACKNOWLEDGEMENT I am most grateful to Almighty God for the grace He has given me to work on this Project, and to the Management of Covenant University for establishing a safe and conducive learning environment through the help of God. I am also grateful to my project supervisor, Prof C.O.A Awosope for his guidance, support, meticulous follow up at the end of each chapter and endless encouragement during my project work. I am grateful to my Parents, Colonel and Mrs. Esther Alao for their financial and moral support and to my Siblings, Kayode and Kolade who, through their several inputs in one way or another have made this project a dream come true. I am grateful to all the technicians that were involved in the project most especially in the hardware coupling as regards welding, bolting e.t.c Finally, a hearty appreciation goes to Kenechukwu Ezenwa, Shelter Orok and all of my friends and colleagues who have contributed to this project in one way or another.
ABSTRACT The Increasing demand for non-polluting mechanized transportation has increased the interest in the use of electric power for personal transportation and also reduced reliance on automobiles. A low cost alternative to an automobile is a bicycle. The rate of improvements in technologies is at an exponential level despite that the electric bicycle is a concept that has been very feasible for years but has not been fully explored. The human electric bicycle is designed to provide electromagnetic propulsions to a bicycle therefore relieving the user of having to produce the energy required to run the bicycle. The system design is based on mechanically coupling a dc motor as the primary power source to drive the bicycle and electrically wiring the motor together with a dc rechargeable battery and applying a programmed micro-controller as a control mechanism for effective and efficient transmission from the source to the motor.
LIST OF ABBREVIATIONS PM – Permanent Magnet MOSFET – Metal-Oxide Semi-conductor Field Effect Transistor EVB – Electric Vehicle Battery GND – Ground OSC – Oscillator PWM – Pulse Width Modulation IC – Integrated Circuit DC – Direct Current ESC – Electronic Speed Control E-Bike – Electric Bicycle IGBT – Insulated Gate Bi-polar transistor
LIST OF SYMBOLS µ - Micro n- Nano m - milli K- Kilo Hz- Hertz A - Amperes V- Voltage s – Seconds f – Farads
CHAPTER ONE INTRODUCTION The electric bicycle is an electrical-assisted device that is designed to provide the electromagnetic propulsions to an existing bicycle therefore relieving the user of producing the energy required to run the bicycle. It contains a strong motor and enough battery power that just requires charging to help in hill climbing, generate greater motoring speeds and provide completely free electric transportation. Electric vehicles cost more and perform worse than their gasoline counterparts. The reason is that mainly because gasoline cars have benefited from a century of intensive development; electric cars have been virtually ignored for several years. Even today, gasoline cars profit from billions of dollars of research every year while electric vehicles receive a tiny fraction of that amount of money.
The primary premise for the Universities‟ support of the electric-powered over the petrol powered has been towards improving air quality, though air quality alone is not a sufficient justification to mandate electric bicycles. The single biggest advantage of electric bicycle is that it is cost effective as it mainly only entails construction cost as running cost would only require the charging of the battery. An Electric bicycle would, however offer other strong benefits that are ignored by the marketplace. These include the dramatic reduction in oil consumption that its widespread use would bring about. Much less oil would be needed because only a tiny proportion of electricity is generated from oil. The other major non-market benefit would be lower greenhouse gas emissions.
1.1 THE PROBLEM DEFINITION
The world‟s car usage is booming. Cars are polluting the environment, dumping increasing amounts of carbon dioxide and other climate-altering greenhouse gases into the atmosphere, and consuming vast quantities of petroleum. The alarming reality is that the automobile usage is beginning to grow at a much faster rate than the
human population, with saturation nowhere in sight. If present trends continue, overtime 3 billion vehicles could be in operation by the year 2050, exceeding 20 cars per 100 people. The problem to be solved is that of increasing the range of a human-powered bicycle by equipping it with an electric motor running off a lithium ion battery thereby reducing the dependency on automobiles.
1.2 MOTIVATION My main motivation of considering this project is that after the thorough study and analysis of being EcoFriendly (Reduce, Reuse and Recycle) during SIWES program. In driving the Chancellor‟s vision of
1 of 10 in 10 by year 2022 wherein two saloon cars and a tri-cycle have
already been developed by the Covenant University Electric Automobile Research Clusters development on what was called the Covenant University Integrated Dual Engine Automobile System (CU IDEA), I have therefore come to a conclusion that an electric bicycle would be Eco-Friendly to the environment and reduce dependency on automobiles and could even encourage the technology on electric transport and will save our world in its way from Global Warming by reducing the CO gases that are usually emitted from automobiles which cause air pollution and are even harmful to the health. I have arrived at the idea of an electric bicycle which would be envisaged as more cost effective as the products listed above. I also observed that there is a very large population of vehicles and not enough road infrastructures to cater for them. This project is a means of providing an alternative for short journeys and also as a recreational facility for persons of all backgrounds and ages. Its importance would include
The elimination of fuel consumption by vehicle users when going on a short distance like running errands.
It‟s effectiveness over a wide range of people and the removal of the burden of the pedaling mechanism typical of normal bicycles.
1.3 AIM AND OBJECTIVES The aim of this project is to incorporate an electromechanical system that would help in propelling a bicycle. To accomplish this aim, the following specific objectives will be achieved:
Simplicity in operation
Effective speed control
Embedded on an existing bicycle
Reasonable power transmission efficiency
Cost efficient in terms of operation
Would ensure air quality
1.4 METHODOLOGY In actualizing the objective of this project above, the electric bicycle will be segmented into two (2) stages. These are
The electrical system design stage
The mechanical coupling stage
The electrical system design stage would include wiring the battery, motor and constructing a speed controlling circuitry to ensure proper travel speed control during the operation of the bicycle. The mechanical coupling includes the proper welding and arrangements of all these components especially the motor and batteries on the framework of the bicycle. This would ensure that it retains a steady standing frame and maintain its balance when in motion.
BATTERY
Fig 1.1 Block diagram of the
MOTOR CONTROLLER CIRCUITRY
BICYCLE WHEEL ROTATION
ELECTRIC MOTOR
CHAIN AND SPROCKET
Electric bicycle construction process
1.5 REPORT ORGANIZATION This project contains five (5) chapters described as follows: The first chapter includes the introduction and the problem definition of the implementation of the design and construction of an electric bicycle. It also discusses the motivation, aims and objectives of the study including the methodology which would be used in the implementation. The second chapter will present the critical analysis of the literature or a segment of the body of knowledge through summary, classification and comparison to prior research studies, reviews of literature, and the theoretical articles in the study. The third chapter will discuss the systems design; this would explain the several design processes that would be used in the implementation of the project.
The fourth chapter will contain the system implementation and Testing; this would explain the actual implementation of the project making use of all the processes to achieve the purpose of the design and also the testing of the project with real life values. The fifth chapter, which is the concluding part of the study, would contain the summary, achievement, recommendation and conclusion.
CHAPTER TWO INTRODUCTION As seen from Chapter 1, the electric bicycle is not a new technology in engineering but has only sought better approaches. This chapter entails the theoretical background and concepts necessary for the proper understanding of the scope of the work carried out in this project and from this to better the design and construction of the proposed Bicycle. It comes from studies of various academic texts, internet write-ups and samples of existing and related project. The information from this review assisted in situating the project in its present context.
2.1 HISTORY OF THE ELECTRIC BICYCLE
Electric bicycle is a bicycle with an electric motor attached to the rear wheel of the bike which generally assists the rider while he or she is peddling. Usually, electric bicycles get their power to drive and run the electric motor from energy stored in electric batteries that are located somewhere within the electric bicycle. These batteries are usually rechargeable by plugging them into a regular household outlet and the batteries are usually stored in a charger when doing so.
Sometime around the year 1898, electric bicycles were documented within various U.S. patents. On 31 December 1895, Ogden Bolton Jr. was granted U.S. Patent 552,271 for a battery-powered bicycle with a 6-pole brush and commutator direct current (DC) hub motor mounted in the rear wheel, there were no gears and the motor could draw up to 100 amperes from a 10-volt battery. One of the first rear wheel electric drive was
implemented by using a belt along the outside of the bike. It wasn‟t much longer than that in which othe r improvements were made to the electric motor itself which proved significant.
In 1897, Hosea W. Libbey of Boston, invented an electric bicycle (U.S. Patent 596,272) that was propelled by a
“double electric motor”. The motor was designed within the hub of the crank set axle. This model was later reinvented and imitated in the late 1990s by Giant Lafree e-bikes.
By 1898, a rear-wheel drive electric bicycle, which used a driving belt along the outside edge of the wheel, was patented by Mathew J. Steffens. Also, the 1899 U.S. Patent 627,066 by John Schnepf depicted a rear-wheel
friction “roller-wheel” style drive electric bicycle. Schnepf's invention was later re -examined and expanded in 1969 by G.A. Wood Jr. with his U.S. Patent 3,431,994 . Wood‟s device used 4-fractional horsepower motors; connected through a series of gears. Despite these improvements, it was not until the 1990s when massive changes occurred in electric motor technology as well as battery technology.
By 2001, the terms “e-bike”,
“power bike”, "pedelec", “pedal-assisted”, “and power-assisted bicycle” were commonly used to refer to e bikes. The term "electric motorbike" or "e-motorbike" refers to more powerful models that attain up to 80 km/h (50 mph).
Since the year 2005, the boom of electric bikes has been phenomenal. Much of this success is due to the fact that the Asian market has been much more active due to the growing affluence in these countries as well as the need for cheaper transportation and less dependence on fossil fuels. In many countries such as India for example, the bicycle itself has been a principal mode of transportation that is very cheap and easy to use. Now, electric bicycles being much cheaper and pollution free are being used in place of fossil fuel.
Some of the less expensive e-bikes used bulky lead-acid batteries, whereas newer models generally used NiMH, NiCd, and/or Li-ion batteries, which offered lighter, denser capacity batteries. Performance varies; however, in general there is an increase in range and speed with the latter battery types.
By 2007, e-bikes were thought to make up 10 to 20 percent of all two-wheeled vehicles on the streets of many major Chinese cities. A typical unit requires 8 hours to charge the battery, which provides the range of 25 to 30 miles (40 to 48 km) at a speed of around 20 km/h. Today, there are literally hundreds of electric bicycles on the market and in the last several years, the electric bike motor as well as the batteries has gotten much more advanced and more capable.
2.2 REVIEWS WITH REFERENCE TO EXISTING WORKS
2.2.1 ELECTRIC ASSISTED BICYCLE
The project was named “Electric Assisted Bicycle” and involved a team consisting of Joe LaPointe and Gregory Huh with each researcher assigned unique tasks throughout the design and implementation stage. The project was a university project and was funded by the Center for Engineering Education and Practice, College of Engineering and Computer Science, University of Michigan-Dearborn. The researchers designed an electric assisted bicycle that extended the range of a typical rider. The system consisted of three source of power: the human effort of the rider peddling the bicycle, electric motor running off a 12-volt lead-acid battery, and a solar panel that can charge the battery when there is adequate sunlight. The power module was controlled by a microprocessor, so that one can operate the bicycle at a preset speed (cruise control). The power control module on the motor will reverse the current in the motor if the speed of the bicycle is more than the desired speed. This current reversal charges the battery, and thus provides regeneration not only when braking but as well as when going downhill, or when the rider pedals harder than the set speed. The final system has features that will appeal to a broad spectrum of users. Those who ride the bicycle for exercise can do so either by disabling the electric assistance or by exerting more effort to generate electric power and charge the battery. Those who would otherwise not use the bicycle to move around the city, can do so, confident that there will be power assistance when they grow tired, or when facing an uphill climb. The constant speed operation will also provide a sense of comfort, especially when coming down steep slopes. Their major motivation was its energy efficiency advantage. This was due to several factors. First, the overall system efficiency taking into account the production of electric power, transmission and distribution, local storage in batteries and conversion of electric power to mechanical motion is estimated to be approximately 50%, while combustion engine vehicles are 15 to 25 percent efficient. Secondly, about 10 percent of the energy used combustion engine vehicles during idling; electric vehicles consume no energy during idling. The goal of the project was designing and building an electric bicycle, powered by a 12-volt battery, with an operating range between 28 to 33 miles. This goal was attained by adding features designed to minimize the power consumption of the system. All the components used for obtaining the goal of the project were small enough to fit on the bicycle.
The first feature was to add pulse width modulation. The advantage of pulse width modulation over the use of adding gears to the system is the fact that with gears torque is gained, but distance efficiency is lost. Pulse width modulation allows the motor to operate at a variety of speeds. In order to obtain the pulse width modulation, a microprocessor can be used to trigger the motor. Since the microprocessor puts out a 5-volt signal at 2 mA, and the motor runs off of 12 volts at a current of 20A, a motor controller must be obtained to handle the voltage and current specifications. To control the speed of a D.C. motor, a variable voltage D.C. power source is needed. However, if a 12-V motor was taken and energized, it will start to speed up: motors do not respond immediately so it will take a small time to reach full speed. If the power is switched off sometime before the motor reaches full speed, then the motor will start to slow down. If the power is switched on and off quickly enough, the motor will run at some speed part way between zero and full speed, this is exactly what a p.w.m. controller does.
If the motor is connected with one end to the battery positive and the other end to battery negative via a switch (MOSFET, power transistor or similar) then if the MOSFET is on for a short period and off for a long period as in A, the motor will only rotate slowly. At B, the switch is on 50% and off 50%. At C, the motor is on for most of the time and only off a short while, so the speed is near maximum. In a practical low voltage controller, the switch opens and closes at a frequency of 20 kHz. This is far too fast for the motor to even realize it is being switched on and off: it thinks it is being fed from a pure D.C. voltage. It is also a frequency above the audible range so any noise emitted by the motor will be inaudible. It is also slow enough that MOSFETs can easily switch on at this frequency. However, the motor has inductance. Inductance does not like changes in
Fig 2.1 MOSFET operation
current. When implement ing the system with a microprocessor, an RC circuit will be used; it as a buffer between the microprocessor and the controller circuit.
2.2.2 IMPROVED AND EFFICIENT ELECTRIC BICYCLE SYSTEM
The project work was named “An improved and efficient Electric Bicycle System with the power of real time information sharing” and involved a team consisting of Chetan Mahadik, Sumit Mahindrakar and Prof. Jayashree Deka. The work was published in the multidisciplinary journal of research in engineering and technology from K.J College of Engineering Pune, India. Many different components were considered in the design of the electric bicycle with several additional features. The power source for the system was given by a dry cell battery. The output of the dry cell battery was 48-V. There were multiple forms of charging source considered such as AC voltage through an outlet, solar energy and mechanical pedal charging system. The source of battery charging was through the photovoltaic solar panel which is light in weight. The solar panel output was 12V and 20 watt. A mechanical pedal charging system was used and dynamo used for the charging system. A dynamo is an electrical generator that produces direct current with the use of a pedal. A dry cell battery block was connected with a controller block. The controller was used to regulate the amount of applied power on brushless DC motor. Also, there are many functions for this controller like over current protection, under voltage protection and also a throttle was used to control the speed of the brushless dc motor. These functions were beneficial to the system and also provided a
solution to any troubleshooting and damages that occurred. The following were considered as the major materials: (i) Brushless DC (BLDC) motor: This is a synchronous motor consisting of armature windings on the stator and permanent magnets on the rotor. The stator of a BLDC motor consists of stacked steel laminations with windings placed in the slots and these stator winding can be arranged in two patterns i.e. a star pattern or delta pattern. The major difference between the two patterns is that the star pattern gives high torque at low RPM and the delta pattern gives low torque at low RPM. There are many advantages of BLDC motor such as better speed versus torque characteristics, high dynamic response, high efficiency, long operating life, noiseless operation, higher speed ranges. The Hall sensors are embedded into the stationary part of the motor. Here, hall sensors are connected with hall sensor magnet to detect the position of rotor. In BLDC motors, the phase windings are distributed in trapezoidal fashion in order to generate the trapezoidal waveform. The commutation technique generally used is trapezoidal commutation where only two phases will be conducting at any given point of time. Typically BLDC motors have three-phase windings that are wound in star or delta fashion and need a threephase inverter bridge for the electronic commutation. The brushless motors are generally controlled using a three-phase power semiconductor bridge. The motor requires a rotor position sensor for starting and for providing proper commutation sequence to turn on the power devices in the inverter bridge. (ii) PIC Controller: The motor controller technique used to control the electric bicycle system was a PIC16F72 controller. There are different functions of this controller such as under voltage protection, over current protection, power supply control, also to drive and control the Brushless dc motor. Different signals were transmitted to the pins of the PIC controller to drive and control the brushless dc motor, such as current detection signal, motor speed control signal, capacity detection system. The PIC16F72 controller has 28 pins, 22 I/O pins that are user configurable on a pin-to-pin basis. There are 35 numbers of instructions in this PIC controller with the operating frequency set at 20 MHz. Also, in this controller were three I/O ports such as PORTA, PORTB and PORTC and three Timers: Timer0, Timer1 and Timer2. In the pin diagram, RA1, RA4 and RA5 pins were used for speed control and current detection signal. The current detection signals were used
here because of any heavy current situation such as when the electric bicycle is running on heavy load thereby causing an increase in the current of the motor which will cause damages to the winding and components of the motor. Also required was the current detection signal for controlling the current, under voltage protection was required to avoid low voltage supply, which affects the normal running operation of the bicycle. (iii) Dynamo: A dynamo is an electrical generator that produces power with the use of a commutator. In this electric bicycle, the dynamo was placed on the front wheel of the bicycle and dynamo commutator was connected at the front wheel of the bicycle. If the bicycle is running then the commutator is rotating and therefore generates the power. In the dynamo, we use a rotating coil of wire and magnet, so it converts
mechanical rotation into an electric current on the basis of Faraday‟s law of induction. A dynamo is a simp le generator that is used to convert mechanical motion into electrical motion with the help of a magnet. It consists of a powerful magnet and pole on which its coil rotates. The rotating coil cuts the line of magnetic force, thereby inducing current to pass through the wire. The mechanical energy produced by the rotation is thus converted into electrical current in the coil. (iv) Solar panel: Here we also use solar panel for generating power. In this bicycle a 20-W solar panel is used and is connected to a 12-V battery this configuration was used for charging the battery. The solar panel converts energy from sunlight directly into electricity through utilization of photovoltaic effect. The solar panel is electrically connected as a module with sheet of glass on top to allow light to pass. This solar panel module was in a series configuration to provide an additional voltage. In solar panel, photons in sunlight hit the solar panel and are absorbed by silicon material. If sunlight is absorbed by silicon then electrons would be excited, if electrons are excited they dissipate the energy and it travels through the cell until it reaches an electron. These electrons are only allowed to move in a single direction.
2.2.3 THE DESIGN, SIMULATION AND CONSTRUCTION OF AN ELECTRIC BICYCLE The project was an undergraduate independent study project by Ben Rogowitz and supervised by Dr. Allison Kipple, Department of Electrical Engineering and Computer Science, Nothern Arizona University In this project a buck converter was selected due to its high efficiency. The controller was based on an MSP430 microcontroller, and then converted to a high speed Pulse Width Modulation (PWM) controller. The customary 10 Amp-hr Nickel-Metal Hydride (NiMH) battery was replaced with a 13.5 Amp-hr Lithium Iron Phosphate (LiFePO4) battery to achieve the final powerful design. Therefore, a 750-W scooter motor with an appropriate chain sprocket was selected, along with accessories to integrate the motor with the existing bicycle. Originally, an MSP430F2012 microcontroller was chosen as the key component of the motor control circuit, primarily due to previous experience with the device. A generic 10Amp diode, two MOSFETs (model #IRF3710 with 100-V, 57-Amp ratings), and line regulators were also used within this circuit. However, the high inrush current from the batteries fused the line regulators in this design, subsequently destroying the microcontroller. The microcontroller was then replaced by a high speed PWM Integrated Circuit (Texas Instruments model #UC3823), and the MOSFETS were replaced by IGBTs (Mouser #40N60A4, 600-V, 75-A ). In addition, a buck converter (Texas Instruments TL2575HV-15, 60-V) with an integrated switch was used in place of the line regulator to provide a constant 15-V for the controller and other circuit components. A few supporting circuit elements were also updated. There were three iterations for the battery component in this design. Initially, two battery packs were composed of inexpensive NiMH batteries (1.2-V, 10 A-hr per cell, 3-A charge rate and 30-A discharge rate). Two packs of 25 cells were soldered together (after 6 hours) to create a
30-V input. Unfortunately, the batteries did not
meet their manufacturer‟s ratings; they overheated at the rated 3 Amp charge, and the array voltage would fall from 30 to 7 Volts under the rated 10 Amp load. After a couple of months, the batteries could no longer hold a charge.
A second battery pack was created with 8.6-V, 3.3 A-hr NiMH batteries. This pack performed well, holding its voltage with a current draw over 30-Amps. However, an LiFePO4 battery system was received (13.5 A-hr, 52V, 60-A current limited, with short circuit protection). Unfortunately, when the limits of the new battery system were tested, a diode failed, and IGBTs then failed under high voltage. The diodes were then upgraded to ultrafast models (Mouser BYT79X-600-127, 600-V, 30-A, trr = 30 ns), the failed IGBTs were replaced, and the final version has worked well ever since. A MATLAB Simulink model of th e electric bicycle‟s final power system design was created. The motor spins at 50 rpm per volt, and the 36-V / 1800 rpm condition was simulated. A resistance of 0.2 Ω and inductance of
200 μH were assumed. Although the simulation did a reasonable job of modeling the real world, the actual system behaved quite differently. In addition, the current flowing through the MOSFET closely resembles an impulse response when the device is turned on, but the simulation did not predict this. The simulation also did not account for the rise and fall times of the IGBT when it was operating in a triode region, when the resistance would increase. Therefore, even though the simulations were educational and provided useful information, they did not completely represent the physical system.
2.3 LEGALITY OF ELECTRIC BICYCLES
Many countries have enacted electric bicycle laws to regulate the use of electric bicycles. Federal regulations, in most countries, now allow up to 20 mph before the electric bicycle will be classified as an unregistered motorcycle. This is actually a very rational and reasonable law and it promotes the development and the usage of good electric bicycles as it enables users of all ages to fully utilize and enjoy the benefits of the electric bicycle with safety precautions in mind.
However, confusion still remains regarding the various laws involving electric bicycles. This stems from the fact that while some countries have national regulations, the legality of road use is left to states and provinces, and then complicated further by municipal laws and restrictions. Furthermore, there is a range of classifications
and terms describing them – "power-assisted bicycle" (Canada) or "power-assisted cycle" (United Kingdom) or
“electric pedal-assisted cycles” (European Union) or simply "electric bicycles". In Nigeria, the Ministry of Transport doesn‟t regulate the electric bicycle as the electric bicycle technology is not a common mean s of transportation yet in Nigeria
2.4 THE FEATURES THAT MAKE UP THE ELECTRIC BICYCLE There are many different components in an electric bicycle. The major components are a bicycle, brushless DC motor, motor controller, dry cell battery.
2.4.1 BICYCLE A bicycle is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other and usually propelled by pedals connected to the rear wheel by a chain and having handlebars for steering and a saddle like seat. Several components that eventually played a key role in the development of the automobile were initially invented for use in the bicycle including ball bearings, pneumatic tires, chaindriven sprocket and tension-spoked wheels. A bicycle rider is called a cyclist or bicyclist. They are till today the principal means of transportation in many regions. They also provide a form of recreation and have been
adapted for use as children‟s toys, general fitness, military and police applications, courier services and bicycle racing. The bicycle‟s invention has had an enormous effect on society, both in terms of culture and of advancing modern industrial method. An electric bicycle (e-bike) is a bike with an electric motor that supports pedalling. A battery powers the motor. With the same amount of energy from the cyclist the e-bike has a higher speed compared to a conventional bicycle. In other words, the cyclist on the e-bike needs to give less energy to reach the same speed as the cyclist on a conventional bicycle.
2.4.2 VEHICLE BRAKING It is very crucial to discuss the available and possible breaking systems to be applied in the electric bicycle. This constitutes the mechanism employed for bringing the motion of the bicycle to a stop. The two major mechanisms are
Regenerative braking
Friction-based braking
2.4.2.1 REGENERATIVE BRAKING
In order
to achieve the regenerative braking, it is essential that (i) the voltage generated by the machine should exceed the supply voltage and (ii) the voltage should be kept at this value, irrespective of the machine speed A regenerative brake is an energy recovery mechanism which slows down a vehicle or object by converting its kinetic energy into another form, which can either be used immediately or stored until needed. This contrasts with conventional braking systems, where the excess kinetic energy is converted to heat by friction in the brake linings and therefore wasted.
The most common form of regenerative brake involves using an electric motor as an electric generator. In electric railways, the generated electricity is fed back into the supply system. In battery electric and hybrid electric vehicles, the energy is stored chemically in a battery, electrically in a bank of capacitors, or mechanically in a rotating flywheel. Hydraulic hybrid vehicles use hydraulic motors to store energy in form of compressed air.
2.4.2.2 FRICTION-BASED BRAKING
This employs the method of applying brake pads to the wheel of the vehicle to restrict the movement or the wheel. It generates a lot of heat and leads to the wearing and tearing of the brake pads.
Friction based-based braking systems are susceptible to „brake fade‟ when used extensively for continuous periods, which can be dangerous if braking performance drops below what is required to stop the vehicle.
2.4.2.3 REGENERATIVE BRAKING WITH FRICTION-BASED BRAKING
The regenerative braking has some limitations, which make it necessary to be used in conjunction with traditional friction-based braking. The reasons are highlighted below:
The friction brake is a necessary back-up in the event of failure of the regenerative brake.
The regenerative braking effect drops off at lower speeds; therefore the friction brake is still required in order to bring the vehicle to a complete halt. Physical locking of the rotor is also required to prevent vehicles from rolling down hills.
Most road vehicles with regenerative braking only have power on some wheels (as in a two-wheel drive car) and regenerative braking power only applies to such wheels because they are the only wheels linked to the drive motor, so in order to provide controlled braking under difficult conditions (such as in wet roads), friction-based braking is necessary on the other wheels.
The amount of electrical energy capable of dissipation is limited by either the capacity of the supply system to absorb this energy or on the state of charge of the battery or capacitors. Effective regenerative braking can only occur if the battery or capacitors are not fully charged. For this reason, it is normal to also incorporate dynamic braking to absorb the excess energy.
Under emergency braking, it is desirable that the braking force exerted be the maximum allowed by the friction between the wheels and the surface without slipping, over the entire speed range from the vehicle's maximum speed down to zero. The maximum force available for acceleration is typically much less than this except in the case of extreme high-performance vehicles. Therefore, the power required to be dissipated by the braking system under emergency braking conditions may be many times the maximum power delivered under acceleration. Traction motors sized to handle the drive power may not be able to cope with the extra load and the battery may not be able to accept charge at a sufficiently high
rate. Friction braking is required to dissipate the surplus energy in order to allow an acceptable emergency braking performance.
For these reasons, there is typically the need to control the regenerative braking and match the friction and regenerative braking to produce the desired total braking effect.
2.5 CONCLUSION
In conclusion, this project is designed to improve the ordinary bicycle and make it more efficient. The electric bicycle is a hybrid and so it can run electrically and can also be pedaled thereby still retaining the exercise people drive from riding bicycle. In the near future, the electric bicycle would be use all over the world because of its numerous advantages.
CHAPTER THREE SYSTEM DESIGN AND IMPLEMENTATION INTRODUCTION This Chapter majors in the design considerations before implementation. The first step that must be taken in design is to accurately and explicitly specify the requirements of the design. The design task involves the selection of the different components of the electric bicycle with appropriate specifications and the supporting circuit necessary for the smooth operation of the bicycle. All circuit diagrams developed have been comprehensively documented in this chapter.
3.1 PROJECT PROCEDURE DESCRIPTION 230-V AC is supplied to charge the electric bicycle battery from a 13-A switch socket outlet. The 230-V AC supply passes through the charging circuit which contains a step-down transformer 230/15-V AC, and this is converted to DC by the bridge rectifier (rectification). The output voltage value is filtered and smoothened by large capacitors, then regulated by the voltage regulating component (LM317T) to produce a 13.8-V dc. The battery output supplies the micro-controller which is PIC18F1320, but the micro-controller utilizes 5-V, hence the 13.8-V input is regulated by the LM7805 voltage regulator to power the micro-controller. This then controls the motor using a LED for indication of switching and speed change. Two relays are connected to the micro-controller to vary the motor speed, when one of the control button is turned on it switches relay 1 and the second control button when turned on does likewise. The motor is rated at 40 Watts with speed 1 at about 25 rpm and speed 2 at about 50 rpm and the number of teeth for the drive gear is 46 while that for the driven gear is 17. Hence for speed 1 at 25 rpm, the bicycle will drive at 67.65 rpm and for speed 2 at 50 rpm the bicycle will drive at 135.3 rpm. The details of these descriptions are well detailed in this chapter.
3.2 DESIGN SPECIFICATIONS TRANSFORMER / RECTIFIER CIRCUIT
Input voltage: 230 V ac Output voltage: 15 V dc BATTERY
Input Voltage: 13.8 V dc Output Voltage: 12 V dc MOTOR
Motor voltage rating: 12 V dc Frequency: 50 Hz Motor power rating: 40 W/0.05 hp Motor speed (No-Load): 45/65 ± 5RPM Motor speed (Load, Speed 1): 20/30 ± 5RPM Motor speed (Load, Speed 2): 40/60 ± 5RPM Weight: 2.1 kg MICRO-CONTROLLER
Input voltage: 5 V OTHER
Gear ratio: 1:3
Control Technology: PIC18F1320
DC SUPPLY
MICROCONTROLLER SPEED CONTROL
Fig 3.1 Block diagram of the system
DC MOTOR
MECHANICAL ROTATION OUTPUT
13.8-V output
Fig 3.2 Circuit Diagram
3.3 THE POWER SUPPLY UNIT Power supply is one of the basic requirements for all electronic appliances. Most electronic devices require dc power sources to be able to function. Batteries are one form of dc source; they are not large and are free of ripples. However, their voltage output is low, frequent replacements are needed due to discharge and they are more expensive than conventional dc power supplies. Most importantly, alternating voltage conversion to dc voltage is possible and very advantageous since ac power supply is economical to produce. For the execution of this project, a 230-V AC supply from the mains was utilized to provide a 15-V DC output. The 15-V DC output was regulated to 13.8 V by current limiting resistors, this was in turn used to power the micro-controller (PIC18F1320) which required only 5 V as its input to control the electric motor rated at 0.05 hp
13.8-V DC output (constant output supply)
230-V AC Mains Input
Transformer 230/15 V AC
Rectifier 15-V pulsating
Filtering
DC
Voltage Regulation 15/13.8 V dc
Fig 3.3 Block diagram of the power supply unit
3.3.1 TRANSFORMATION A transformer is a device that transfers electrical energy from one circuit to another by the use of electromagnetic induction. It is a static (or stationary) electro-magnetic passive electrical device that works on
the principle of Faraday‟s law of induction by converting electrical energy from one form to another. Transformers are capable of either increasing or decreasing the voltage and current levels of their supply, without modifying its frequency, or the amount of electrical power being transferred from one winding to another via the magnetic circuit. There are two types of transformer namely: Step-up transformer: Provides an output voltage that is higher than the input voltage. Step-down transformer: Provides an output voltage that is lower than the input voltage For the execution of this project, a step-down transformer was used to step down a 230-V supply to a 15-V supply which is an unregulated and alternating voltage.
3.3.2 RECTIFICATION Rectification is the process of converting an alternating ac voltage to a pulsating dc voltage. In this application of rectification, a full wave bridge of four diodes incorporated into a single electronic was used . During the positive half of the input voltage cycle, D1 and D4 are forward biased; D3 and D4 are reverse biased. During the negative half-cycle, D2 and D3 are forward biased.
Fig 3.4 Full wave bridge rectifier
In the full-wave rectifier, there is a voltage drop of 1.4 V which is as a result of the 2 diodes which are always present at the conduction path of each cycle. When a voltage greater than 1.4 V is across the rectifier circuit, D1
and D4 are forward biased and current starts to flow through D1 to the load and to the ground, then up from the ground through D4 to the lower part of the transformer. At this stage, D2 and D3 are reversed biased and thus only negligible leakage current will flow through. This implies D2 and D3 do not allow current to pass through in the opposite direction and thus the diodes behave like a switch. At the opposite half cycle, D2 and D4 are now forward biased, thus current flows out of the lower part of the transformer through D2 to the load and then to the ground and also up from the ground to the upper part of the transformer through D4, D1 and D3 are now reverse biased. Rectification analysis
= maximum value of voltage = average value of load voltage = peak value of half wave = root mean square value of the output voltage = 12-v = x √2 = 12 x √2 = 16.971-V = - = 16.971-V – (2 x 0.7) = 15.571-V = (2 x ) = 9.913 = √2 = 11.01-V
Allowable ripple factor = √ ( ^2 - ^2) Allowable ripple factor = (√ (11.01)^2 – (9.913)^2 (9.913) = 0.483 The output of the rectifier is a rippled DC which can damage digital circuits. Therefore, a filter circuit is introduced to smoothen the ripple.
3.3.3 FILTERING This is also known as smoothening and can be defined as the removal of pulsations found in the output voltage. Smoothening is performed by an electrolytic capacitor which has a large value connected across the supply to act as a reservoir, sending current to the output when changing DC (dotted line) and the smoothed DC (solid line). The capacitor charges rapidly near the peak of the changing DC, and then discharges as it supplies current to the output.
Fig 3.5 Smoothening
Filtering increases extensively the average value of DC voltage to almost the peak value (1.4 x RMS value). Smoothening is not perfect due to the capacitor voltage reducing a little as it discharges, providing a small ripple voltage. For most circuits, a ripple which of 20% of the supply voltage is acceptable and the equation below gives the required value for the smoothening capacitor. A large capacitor will provide fewer ripples at its output. The value of the capacitor must be doubled when smoothening half-wave DC. Selecting a filtering capacitor
Allowable ripple factor = 20% of ripple effect, = 12V (no load voltage) =
x √2 = 12 x 1.414 = 16.968 V
The ripple voltage, = x Ripple % = 16.968 x 0.20 = 3.3936 V The time interval for charging pulses (T) Ripple frequency = = 2f, where f = 50 Hz Time (t) = 1/2f = 1/(2 x 50) = 0.01-s = 10 ms Therefore, C = ( x t) / () where C = capacitance {in microfarads (µF)} = 0.5-A t = 0.01-s C = (0.5 x 0.01) / (3.3936) = 1473 µF Voltage rating of the capacitor = =
x √2 = 16.968 x 1. 414 = 23.99 V
Hence, the best choice practically will be a 100-F, 24-V capacitor. However the magnitude of the ripple voltage can be further cut down if a capacitor with a larger value is used, this would cause a reduction in the on time of the conducting pair of diodes which automatically makes the surge time of the diode excessive.
3.3.4 VOLTAGE REGULATION A voltage regulator is designed to automatically maintain a constant voltage level. It provides the functions of pass element, voltage reference, and protection from overcurrent in one package. It may use an
electromechanical mechanism, or electronic components, depending on the design; it may be used to regulate one or more AC or DC voltages. The voltage regulator has the primary function of keeping the terminal voltage of the DC supply constant when the ac input voltage to the transformer changes or the load varies. For the purpose of this project, an IC voltage regulator LM317T was used for voltage regulation at the power supply unit to regulate the voltage from 15 V to 13.8 V to charge the battery and the LM7805 was used to regulate the voltage output from the battery from 12 V to 5 V that was used to power the micro-controller.
3.4 BATTERY UNIT A battery is a device that converts chemical energy directly into electrical energy. It consists of a number of voltaic cells; each voltaic cell consists of two half-cells connected in series by a conductive electrolyte containing cations and anions. The 12-V lead acid battery was selected for the actualization of this project due to its following advantages:
Improved energy density (up to 40 percent greater than nickel-cadmium cells) which can be translated into either longer run times from existing batteries or reductions in the space necessary for the battery.
Elimination of the constraints on cell manufacture, usage, and disposal imposed because of concerns over cadmium toxicity
Simplified incorporation into products currently using nickel cadmium cells because of the many design similarities between the two chemistries.
3.5 THE MICRO-CONTROLLER UNIT
Peripheral Interface Controller or Programmable Intelligent Computer (PIC) is a family of the modified Harvard architecture microcontrollers made by Microchip Technology, derived from the PIC1650 which was srcinally developed by General Instrument's Microelectronics Division.
PICs are popular with both industrial developers and hobbyists alike due to their low cost, wide availability, large user base, extensive collection of application notes, availability of low cost or free development tools, and serial programming (and re-programming with flash memory) capability.
The PIC architecture has the following features:
Separate spaces for code and data (Harvard architecture).
A small number of fixed-length instructions.
Most instructions are single-cycle (2-clock cycles, or 4-clock cycles in 8-bit models), with one delay cycle on branches and skips.
One accumulator .
All RAM locations function as registers as both source and/or destination of math and other functions.
A hardware stack for storing return addresses.
A small amount of addressable data space (32, 128, or 256 bytes, depending on the family) which could be extended through banking.
Data-space mapped CPU, port, and peripheral registers.
ALU status flags are mapped into the data space.
The program counter is mapped into the data space and is writable.
Their advantages include the following:
Small instruction set to learn
Reduced Instruction Set Computer (RISC) architecture
Built-in oscillator with selectable speeds
Easy entry level, in-circuit programming plus in-circuit debugging PICKit units available for less than $50
Inexpensive microcontrollers
Wide range of interfaces including I²C, SPI, USB, USART, A/D, programmable comparators, PWM, LIN, CAN, PSP, and Ethernet
Availability of processors in DIL package makes them easy to handle for hobby use.
Their Limitations include the following:
One accumulator
Register-bank switching is required to access the entire RAM of many devices
Operations and registers are not orthogonal; some instructions can address RAM and/or immediate constants, while others can use the accumulator only.
3.5.1 PIC18F1320 MICRO-CONTROLLER
This microcontroller has nano-Watt (nW) Technology, which features six enhanced power-managed "software controlled" modes, power consumption as low as 0.1 micro-amps (µA) in standby mode and a wide operating voltage ranging from 2 volts to 5.5 volts which makes this device ideal for battery managed applications. This device also encompasses a new low-current watchdog timer, a 2-speed start-up from a reset or sleep mode and a new fail-safe clock monitor that is used to detect an external clock failure. This powerful 10 Million Instruction Per Second MIPS (100 nanosecond instruction execution) yet easy-to-program (only 77 single-word instructions) CMOS FLASH-based 10-bit microcontroller packs Microchip's powerful PIC® architecture into an 18-pin package and is upwards compatible with the PIC16C5X, PIC12CXXX, PIC16CXX and PIC17CXX devices and thus providing a seamless migration path of software code to higher levels of hardware integration. The PIC18F1220 features a 'C" compiler friendly development environment, 128 bytes of EEPROM, Selfprogramming, an ICD, capture/compare/PWM functions, 7 channels of 10-bit Analog-to-Digital (A/D) converter, Addressable Universal Asynchronous Receiver Transmitter (AUSART) and Advanced Low Power Oscillator controls. All of these features make it ideal for battery powered and power consumption critical applications including instrumentation and monitoring, data acquisition, power conditioning, environmental monitoring, telecom and consumer audio/video applications.
Its features include:
Low-Power Features include the following
- RUN: CPU on, peripherals on - PRI_RUN: 150 µA, 1 MHz, 2V - Timer1 Oscillator: 1.1 µA, 32 kHz, 2V - Watchdog Timer: 2.1 µA - Two-Speed Oscillator Start-up Peripheral Features
- High current sink/source 25 mA/25 mA - Three external interrupt - Enhanced Capture/ Compare/ PWM (ECCP) module - Compatible 10-bit, up to 13-channel Analog-to-Digital Converter module (A/D) - Supports RS-485/RS-232 and LIN 1.2
Special Microcontroller Features are
- Priority levels for interrupts - 8 x 8 Single-Cycle Hardware Multiplier - Programmable period from 41 ms to 131s - 100,000 erase/write cycle Enhanced FLASH program memory typical - 1,000,000 erase/write cycle Data EEPROM memory - Self-reprogrammable under software control - Single supply 5V In-circuit Serial Programming via two pins - In-Circuit Debug (ICD) Oscillators
- Four Crystal modes
- Two external RC modes, up to 4 MHz - 8 user-selectable frequencies - Secondary oscillator using Time1@ 32 kHz - Fail-Safe Clock Monitor
Fig 3.6 PIC18F1320 Pinout description
Electrical characteristics
Maximum output current sunk by any I/O pin = 25mA
Minimum output current sourced by any I/O pin = 25mA
Fig 3.7 PIC18F1320 Outer structure
3.6 OTHER COMPONENTS UTILIZED 3.6.1 RESISTORS A resistor is a two-terminal electronic component that produces a voltage across its terminals that is
proportional to the electric current passing through it in accordance with ohm‟s law V=IxR The formula for calculating resistance is given by R = V/I The function of the resistor in both the charging and control/switching circuits is for current limiting.
3.6.2 CAPACITORS A capacitor, which is a passive electronic component, consists of a pair of conductors which are separated by a di-electric. A capacitor has good similarities with a battery, but charges and discharges more efficiently. An ideal capacitor is characterized by a constant capacitance C, defined as the ratio of charge +/- Q on each conductor to the voltage V between them. i.e C = Q/V Large capacitors are used in the battery charging unit for filtering and elimination of pulses, while they are used in the micro-controller unit for the oscillator.
3.6.3 SWITCHING CIRCUIT (RELAY)
This is the part of the circuit under the control of the micro-controller. The function of this circuit is to switch on/off the external load and regulate it to its different speeds. When mains power supply is available, the load is powered and the signal sent to the micro-controller. Electromechanical relays are electro-magnetic devices that convert a magnetic flux generated by the application of a low voltage electrical control signal either AC or DC across the relay terminals, into a pulling mechanical force which operates the electrical contacts within the relay
Fig 3.8 Relay Components
The 12-V, 30-mA relay with a coil resistance of 300Ω was used Choosing the base resistor
V+ = 12 V (relay voltage from regulated dc supply) = 0.7 V (silicon) = 5 V (from micro-controller) = (collector resistance)
V+ = + = + = -
where = collector current = base current = input voltage V+ = supply voltage = collector-emitter voltage = 0-V (at saturation mode)
3.6.4 INTEGRATED CIRCUIT (ULN2003)
The ULN2003A is a high-voltage, high-current Darlington transistor array which consists of seven NPN Darlington pairs that feature high-voltage outputs with common-cathode fly-back diodes for switching inductive loads.
The drivers can be paralleled for higher current capability, even stacking one chip on top of another, both electrically and physically has been done. Generally, it can also be used for interfacing with stepper motor, where the motor requires high ratings which cannot be provided by other interfacing devices.
Features include
500-mA rated collector current (single output)
50-V output
Includes output fly-back diodes
Inputs compatible with various types of logic
Applications include In driving
Relays
Lamps LED displays Stepper motors
Fig 3.9 UNL2003 Pinout diagram
Fig 3.10 ULN2003 Outer structure
3.6.5 LIGHT EMITTING DIODE (LED) This is a forward-biased P-N junction that emits light through spontaneous emission by a phenomenon termed
“electroluminescence”. In this project, a LED was used for the indication of switching and control speed. The different indicators that were established include - Light ON: This would indicate that the motor is off - Light OFF: This would indicate that the motor is on, it can be indicated in either form as below:
(i) Slow Twinkle: This would indicate that the motor is on speed 1. (ii) Fast Twinkle: This would indicate that the motor is on speed 2. The value of the resistor R is obtained using the equation
R = ( )/ I where: = supply voltage = LED voltage (usually 2 V, but 4 V for blue and white LEDs) Hence, since the LED used in this project was blue, then = 4 V I = LED current It is ideal to choose a LED whose current is less than the maximum current allowed, so as to prevent damage to the LED; resistor R acted as a current limiting resistor and was connected in series with the LED
3.6.6 GEAR
A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part to transmit torque, in most cases with teeth on the one gear being of identical shape, and often also with that shape on the other gear. When two gears mesh, and one gear is bigger than the other (even though the size of the teeth must match), a mechanical advantage is produced, with the rotational speeds and the torques of the two gears differing in an inverse relationship. When two gears mesh, the smaller gear usually rotates faster than the larger gear though the larger torques gear is still proportionally greater.
In transmissions with multiple gear ratios such as bicycles, motorcycles and cars, the term “gear” refers to a gear ratio rather than an actual physical gear.
Fig 3.11 A 76 teeth Gear
3.6.6.1 GEAR RATIO
The gear ratio of a gear train, also known as its speed ratio, is the ratio of the angular velocity of the input gear to the angular velocity of the output gear. The gear ratio can be calculated directly from the numbers of teeth on the gears in the gear train. The torque ratio of the gear train, also known as its mechanical advantage, is determined by the gear ratio. The speed ratio and mechanical advantage are defined so they yield the same number in an ideal linkage 3.6.6.2 GEAR TRAINS WITH TWO GEARS
The simplest example of a gear train has two gears and that is the type used for the implementation of this project. The "input gear" (also known as drive gear) transmits power to the "output gear" (also known as driven gear). The input gear will typically be connected to a power source, such as a motor or engine. In such an example, the power output of the output (driven) gear depends on the ratio of the dimensions of the two gears.
Mathematically, if the input gear GA has the radius rA and angular velocity of radius rB and angular velocity ωB , then
............................(i)
ωA
, and meshes with output gear GB
The number of teeth on a gear is proportional to the radius of its pitch circle, which means that the ratios of the gears' angular velocities, radii, and number of teeth are equal.
NA
is the number of teeth on the input gear and NB
is the number of teeth on the output gear. The following equation is formed:
……………………(ii) This shows that a simple gear train with two gears has the gear ratio R given by
………………..……(iii) This equation shows that if the number of teeth on the output gear
GB
is larger than the number of teeth on the
input gear GA, then the input gear GA must rotate faster than the output gear
GB.
For the implementation of this project, a 46-teeth gear was used as the drive and a 16-teeth gear as the driven; hence the ratio would be 1:2.8, therefore from equation (iii) above, we have
Gear ratio = 50 = 17
46
Hence, = 135.3 rpm
From this deduction, we can observe that the gear attached to the bicycle (driven gear) would rotate about 2.8 times faster than the gear attached to the motor (drive gear).
3.7 CONCLUSION This chapter discussed the system design and processes required for the realization of the project.
CHAPTER FOUR IMPLEMENTATION AND TESTING INTRODUCTION This Chapter discusses the project implementation, construction and the various testing methods adopted. It introduces the mechanism used in running the bicycle and the testing methods applied.
4.1 IMPLEMENTATION The Project construction was divided into the following three (3) main categories:
Construction of the speed controller circuit.
Mounting and welding of devices.
Electrical wiring of the system.
4.1.1 SOFTWARE IMPLEMENTATION This entails the coding of the speed and switching control circuit on the PIC18F1320 micro-controller before burning of the codes.
Fig 4.1 Interface of the compiler (mikroC PRO for PIC)
4.1.2 HARDWARE IMPLEMENTATION The hard ware implementation of this project entails the mounting, welding of devices and the electrical wiring of the system.
4.1.2.1 MOUNTING AND WELDING OF DEVICES
Prior to construction, a moderately sized bicycle which could withstand the weight of the modules that was to be constructed on it is required.
Fig 4.2 Bicycle prior to mounting of electrical features and mechanical coupling
Fig 4.3 Mounting of an additional sprocket for motor driving
Fig 4.4 Sprocket Coupling on the back wheel
Fig 4.5 Gear connection of the sprocket and motor via a power chain
Fig 4.6 Mounting of the d.c motor and battery on the bicycle
4.1.2.2 ELECTRICAL WIRING OF THE SYSTEM This involves the electrical wiring of all the battery, speed controller and the motor together
Fig 4.7 Package for power supply unit, micro-controller unit circuits
4.2 TESTING This section is concerned with the tests that were carried out to verify and monitor the operation and performance conditions of the electric bicycle. This involves the following tests as they relate to this system:
Unit Testing
Integration Testing
System Testing
4.2.1 UNIT TESTING The electric bicycle composes of different units coupled together to make up the whole system. Tests on units independent of one another were carried out such as the resistance and capacitance values before circuit connection, the d.c motor to ensure the required revolutions per minute on no-load, the d.c battery to ensure the required voltage output, the speed and switch controller and the bicycle itself to ensure optimum operating conditions before the various components were mounted on it.
4.2.1.1 POWER SUPPLY UNIT TEST The power supply unit consists of a switch, step-down transformer rated 230/12 V, a diode bridge, a capacitor and a voltage regulator output. All tests were carried out at the various outputs of these components to ensure the required wave form in cases of a.c or pulsating d.c and the expected voltage output as the case maybe. All outputs were tested with a multi-meter and oscilloscope
4.2.1.2 MICRO-CONTROLLER UNIT TEST Micro-controllers are powered with 5 V dc with their output also at 5 V, the battery voltage that should be feeding the micro-controller is to be a little above 6 V dc. The micro-controller also acts as a switching, controlling device and was monitored to ensure it performed its switching, controlling function for every time the control button was pressed.
The different switching, control levels were indicated in this project using a blue-colored LED.
Fig 4.9 LED indicator at OFF
Fig 4.10 LED indicator at ON
4.2.1.3 MECHANICAL BICYCLE TEST The bicycle itself was tested mechanically to ensure optimum operating conditions of the wheels, tyres and brakes e.t.c before the various components were mounted on it.
4.2.2 INTEGRATION TESTING Integration testing was carried out to evaluate the interaction between distinct and separate modules or stage of the project. This was necessary as the project involved integration of several components and binding them together to form a complete system. The successful interaction between these units ensured the successful implementation of the system all together. The integration tests in this project include the following:
The test was about connecting the power supply unit to the battery, the battery connected to the microcontroller unit then to the motor
The test was about the coupling of the motor to the rear wheel
4.2.3 SYSTEM TESTING System testing was done to test the complete bicycle. This test involved the complete operation of the system based on the interaction between the several modules. This involved riding the bicycle electrically with the aid of the d.c motor, the battery and the varying the system speed using the speed controller.
4.3 OVERVIEW OF TESTING INSTRUMENTS
The implementation and testing phase required the use of several testing instruments and equipment such as
OSCILLOSCOPE: The oscilloscope is a device that is used to generate the waveforms of
corresponding component outputs. It was used to determine and confirm the pulse signals generated by the circuit for a.c and pulsating d.c signals.
DIGITAL MULTIMETER: The digital multi-meter is used to measure resistance, frequency, a.c or
d.c voltage and current. It was very critical in the process of implementing the design on the Vero-board for the measurement of parameters like voltage, current and resistance values of components, continuity and in some cases frequency measurement. The digital multi-meter was handy throughout the entire construction as its use couldn‟t be over emphasized.
4.4 BILL OF QUANTITY COMPONENT
UNIT
UNIT PRICE (NGN)
PRICE (NGN)
Bicycle
1
15,000
15,000
12v dc battery
1
12,000
12,000
DC Motor
1
10,000
10,000
PIC18F1320
1
2,000
2,000
ULN2003 IC
1
150
150
Relay
2
250
500
Transformer
1
250
250
Switch/Control button
2
30
60
Resistor
4
10
70
Microcontroller
Capacitor
1
40
40
Voltage Regulator
2
110
220
Vero board
2
50
100
Power chain and Gear
1
2,000
2,000
Controller case
1
200
200
Mounting and
5,000
welding Miscellaneous
5,000
Expenses Transportation
3,000
TOTAL
55,590
4.5 CONCLUSION In conclusion, the implementation and testing phase were very successful and the design specifications were fully realized.
CHAPTER FIVE CONCLUSION 5.1 MAJOR AIM The fundamental aim of this project is to incorporate an electromechanical system unto an existing bicycle frame to power the bicycle without damaging the structural balance and rotor abilities of the bicycle. This section shall begin with a summary of the approach taken, the challenges faced and the recommendations for future direction of this project.
5.2 SUMMARY The present available technology has made it possible for the actualization and the full implementation of the project. The PIC microcontroller technology was implemented as the control technology over the Pulse Width Modulation (PWM). The system was developed to serve as assistance and not for full mobility. This technology is pollution free and is capable of operating with a very low cost.
5.3 ACHIEVEMENTS The project has been able to realize the following accomplishments:
The normal bicycle pedaling function is retained and fully functional.
The embedded devices were properly customized on an existing bicycle with the frame still intact.
Simplicity of operation: the system operates a simple on/off switch mechanism and for speed control 1/2 depending on the speed required, 1 for a low speed and 2 for a higher
Power transmission efficiency.
5.4 CHALLENGES ENCOUNTERED
The challenges encountered during the design and implementations of this project are as follows:
Some of the electronic components got damaged during soldering.
The programming of the micro-controller operation in C# was quite challenging.
Mechanical coupling of the bicycle needed a lot of manual labor and I only had a technician for assistance.
Difficulty in balancing cost and functionality.
It was not an easy task in determining, for example, the right motor, gear ratio, battery output required as it required lots of analysis and calculations.
5.5 KNOWLEDGE ACQUIRED I have gained adequate and valuable understanding on how to design and analyze electric circuits with a fundamental understanding of the various electronic components in an electric circuit. In terms of the dc motor controller system used which was a micro-controller; I have been able to understand the fundamentals of a micro-controller and programming in C# I now have a sound understanding of project management as it entails time, budget available and delivery according to the initial specifications.
5.6 RECOMMENDATIONS Even though the system seems to have achieved the basic requirements of an electric bicycle, there is need for possible further research. Some of the observations include
Incorporation of a hub wheel motor: The hub wheel motor is an electric motor that is incorporated onto the hub of a wheel and drives it directly. Compared with other conventional motors, its advantages include the following (i)
Energy efficiency: This is the biggest advantage of a hub wheel motor. A conventional vehicle uses mechanical means to transmit power from a centrally mounted engine/motor to the wheels.
Hence, loses occur due to heating from the friction and through the transmission system. An electric motor mounted directly inside a wheel without any mechanical transmission will avoid all such losses. (ii)
Reduced weight: due to the motor being mounted directly inside the wheel, the weight of the system is reduced because no structural and transmission parts are used.
Solar cell battery charger: the application of a solar cell battery charger can make the electric bicycle
more mobile than it currently is because it gives access to electricity for recharging anywhere there‟s sunlight.
Upgrading to a higher voltage system and retaining system weight: A 36-V or even 48-V system would be more stable and would be a lot better than the 12 V used as the current drawn by the motor will be low. The 12-V system has a low power and the current drawn was high. Higher current value creates more heat and a much bigger motor controller. Thus, a system with a higher voltage would draw a lower current and hence reduce the head produced in the speed control circuit.
5.7 CONCLUSION In conclusion, it should be noted that the Electric Bicycle should not be relied on completely for transportation as it mainly only serves as an assistance to the pedaling system.
REFERENCES
[1] B.L Theraja and A.K Theraja “A textbook of electrical technology” S chand & company, India, 2006 [2] B. Kumar and H. Oman, “Power control for battery-electric bicycles,” National Aerospace and Electronics Conf., vol. 1, May 24–28, 1993. [3] Ben Rogowitz and Dr. Allison Kipple “The Design, Simulation, and Construction of an Electric Bicycle”, Department of Electrical Engineering & Computer Science, Northern Arizona University
[4] Hope, O.E “Programmable Logic Controller (PLC)”, unpublished B.Eng Lecture Notes. Covenant University, Ota, 2012. [5] Joe LaPointe and Gregory Huh “Electric Assisted Bicycle”, Center for Engineering Education and Practice, College of Engineering and Computer Science, University of Michigan-Dearborn [6] History of the Electric Bicycle [online] Available at: [7] Chetan Mahadik, Sumit Mahindrakar and Prof. Jayashree Deka “An Improved & Efficient Electric Bicycle system with the Power of Real- time Information” [8] James, O.S “Electric Drives”, unpublished B.Eng. Lecture Note Covenant University, Ota, 2012. [9] Song Jie Hou, Yoichiro Onishi, Shigeyuki Minami, Hajimu Ikeda, Michio Sugawara, and Akiya Kozawa
“Charging and Discharging Method of Lead Acid Batteries Based on Intern al Voltage Control” [10] PIC Microcontroller [online]: Available at [11] Braking [online] Available at:
[12] Electric Bicycle Laws [online] Available at: < en.wikipedia.org/wiki/Electric_bicycle_laws>
[13] PIC18F1320 [online] Available at: < http://www.futurlec.com/Microchip/PIC18F1320.shtml>
APPENDIX A SOURCE CODE
CODE FOR SWITCHING ON/OFF AND CONTROLLING MOTOR SPEED
sbit LED1
at LATB5_bit;
sbit LED1_Direction at TRISB5_bit;
sbit MOTOR_SPEED_2
at LATA3_bit;
sbit MOTOR_SPEED_2_Direction at TRISA3_bit;
sbit MOTOR_SPEED_1
at LATB0_bit;
sbit MOTOR_SPEED_1_Direction at TRISB0_bit; char blink_counter = 0;
enum STATE{OFF =0, SPEED_1, SPEED_2};
char i; char machine_state = OFF;
void Interrupt(){ if (TMR0IF_bit){ TMR0IF_bit = 0; TMR0H
= 0x3C;
TMR0L
= 0xB0;
blink_counter++;
switch(machine_state){ case OFF: MOTOR_SPEED_1 = 0; MOTOR_SPEED_2 = 0; LED1 = 0;
break;
case SPEED_1:
if(blink_counter>6){ LED1 = ~LED1; MOTOR_SPEED_1 = 1; MOTOR_SPEED_2 = 0; blink_counter =0; }
break;
case SPEED_2:
if(blink_counter>=1){ MOTOR_SPEED_1 = 0; MOTOR_SPEED_2 = 1; LED1 = ~LED1; blink_counter =0; }
break;
default: machine_state = OFF;
}
} }
void InitTimer0(){
T0CON
= 0x82;
TMR0H
= 0x3C;
TMR0L
= 0xB0;
GIE_bit
= 1;
TMR0IE_bit
= 1;
}
void main(){ LED1_Direction = 0;//OUTput direction MOTOR_SPEED_1_Direction = 0; MOTOR_SPEED_2_Direction = 0;
MOTOR_SPEED_1 = 0; MOTOR_SPEED_2 = 0; LED1 = 0;
IRCF0_bit = 1; IRCF1_bit = 1; IRCF2_bit = 1; TRISB4_bit = 1;// configure button pin as input ADCON1 = 0x70;// port b is all digital InitTimer0();
while(1){
if (Button(&PORTB, 4, 20, 0)){ // check button STATE machine_state++; Delay_ms(500);
}
}
}
