implementation of dc motor driven electric …

i

A PROJECT REPORT

on

IMPLEMENTATION OF DC MOTOR DRIVEN

ELECTRIC SKATEBOARD USING SVPWM

Submitted in partial fulfillment for the award of the degree

of

BACHELOR OF TECHNOLOGY

in

ELECTRICAL AND ELECTRONICS ENGINEERING

by

THOKCHOM ANKIT SINGH (Reg. No.: RA1511005010119)

ANAMIKA RANJAN (Reg. No.: RA1511005010179)

JATIN SINGH (Reg. No.: RA1511005010199)

Under the guidance of

Mr. R. PALANISAMY, M.TECH., (Ph.D)

Associate Professor, EEE

FACULTY OF ENGINEERING AND TECHNOLOGY

SRM Nagar, Kattankulathur- 603 203

Kancheepuram Dist

MAY 2019

ACKNOWLEDGEMENTS

We would like to express my gratitude to our respected Director (E&T),

Dr.C.MUTHAMIZHCHELVAN for their encouragement towards our growth and

activities.

I extend my sincere gratitude to Professor and Head of EEE Department,

Dr.K.VIJAYAKUMAR, SRM Institute of Science and Technology, Kattankulathur for

his commendable support and encouragement towards the completion of project with

perfection.

I owe my deep sense of gratitude to my Project Coordinator,

Mr.A.SURESHKUMAR, Assistant Professor having extended their fullest support in

completing the project work.

I whole heartily thank to my guide, Mr.R.PALANISAMY, Assistant Professor,

Department of Electrical and Electronics Engineering for standing by my side during the

hard days and being my Guide for this project.

I would also like to thank the various personnel from mechanical and electronics

department, and Fabrication Lab who assist us with the hardware implementation of our

project and working with us day and night to make this project a success.

Last but not the least; I would like to thank my Parents and Friends for the

supports, concerns and prayers, which were a major factor in the completion of this project.

(THOKCHOM ANKIT SINGH)

(ANAMIKA RANJAN)

(JATIN SINGH)

ABSTRACT

Several problems are faced by today’s generating stations. One of them is the increase in

pollution in everyday life. Each of us can play a part in reducing this by using some

environmentally friendly method such as cycles which requires mechanical force. Another

way to accomplish this is by using electricity to produce this mechanical force i.e. electric

motors. The concept is new-fangled as compared to the cycle and it instils the features of

being more convenient, cheaper and low maintenance. In this project, we are making an

electric skateboard. Using pulse width modulation or PWM to control the motor and

connecting the motor with a skateboard. PWM circuit is used and improvised according to

our own need for higher voltage. This will further be controlled by space vector (SVPWM)

algorithm to increase its efficiency. Along with these the basic concept of skateboard parts

is studied and manipulated so as to run a motor with its help. The skateboard is fabricated

by keeping in mind the roads of India so that it can run on rough terrain, not only on well-

developed roads. To solve this problem a ground clearance is provided which meets our

requirement. Similarly, conventional skateboard wheels are not used so as to modify the

initial project.

TABLE OF CONTENTS

CHAPTER TITLE PAGE NO.

ABSTRACT iii

LIST OF FIGURES v

LIST OF TABLES v

1. INTRODUCTION 1

1.1. GENERAL 1

1.2. METHODOLOGY 2

1.3. BLOCK DIAGRAM 2

1.4. EXPLANATION OF BLOCK DIAGRAM 3

1.5. LITERATURE SURVEY 3

1.6. INFERENCE FROM LITERATURE SURVEY 6

1.7. PROPOSED OBJECTIVE 6

2. PULSE WITH MODULATION 7

2.1. INTRODUCTION TO PULSE WIDTH MODULATION 7

2.2. TYPES OF PULSE WIDTH MODULATION 8

2.3. SPACE VECTOR PULSE WIDTH MODULATION 8

2.4. SVPWM VS PWM 10

2.5. APPLICATIONS 10

3. WORKING PRINCIPLE 12

3.1. CIRCUIT DIAGRAM 12

3.2. MODIFIED CIRCUIT DIAGRAM 14

4. MATHEMATICAL MODELLING 15

4.1. FRICTION CALCULATION 15

4.2. CURRENT LIMITER CALCULATION 16

4.3. TRUCKS 17

5. SOFTWARE SIMULATION 18

5.1. ELECTRONICS 18

5.2. MECHANICAL 20

6. HARDWARE 24

iv

7. RESULT AND DISCUSSIOIN 31

7.1. RESULT OF SIMULATION 31

7.2. RESULT DISCUSSION 34

8. CONCLUSION 35

8.1. CONCLUSION 35

8.2. FUTURE SCOPE 35

REFERENCES 36

v

LISTS OF TABLES

TABLE TITLE PAGE

2.1 Vector table for switch combination and voltage output 10

vi

LISTS OF FIGURES

FIGURE TITLE PAGE

1.1 Block diagram showing control flow of

DC motor 3

2.1 Change in pulse width causes change in

average voltage level 8

2.2 Space vector diagram representing six

Sectors 10

3.1 Basic 555 timer circuit for PWM 11

3.2 555 timer internal logic circuit 11

3.3 Modified 555 timer PWM circuit 14

4.1 Trucks working 16

5.1 Simulation diagram 19

5.2 Schematic diagram 19

5.3 MATLAB simulation diagram 20

5.4 Motor mount back view 20

5.5 Motor mount front view 21

5.6 Skateboard 21

5.7 Skateboard with motor mount 22

5.8 Sprocket isometric view 22

5.9 Sprocket top view 23

6.1 Bread board 24

6.2 Trucks component 24

6.3 Truck component 25

6.4 Wheel assembly front view 25

6.5 Wheel assembly back view 26

6.6 Skate Board Deck 26

6.7 Trucks wheel assembly 27

6.8 CNC machine constructing sprocket 27

6.9 Motor mount and wheel assembly 28

vii

6.10 Isometric view 28

6.11 Electric Skateboard side view 29

7.1 Potentiometer at 15% 30



7.4 MATLAB output 31

7.5 Speed controller PCB 32

1

CHAPTER 1

INTRODUCTION

1.1 GENERAL

Pulse Width Modulation is a technique of modulation of the digital pulses. This

method is used for controlling the power supply to any device. This is achieved by changing

the sweep of the pulses. The ON and OFF time of the circuit is modified accordingly. The

on and off time control the output voltage and thus help in controlling the connected device.

This method of output voltage control is being used to modify the speed of the DC motor

for this project. The time period for which a device conducts is called as the ON time of the

device. Similarly, the time period when the device does not conduct is called the OFF period.

The ratio of this ON time to the entire time period is called as the Duty Ratio.

In our project, we attempt to change duty ratio of the PWM circuit and feed it to the

motor. The change in duty cycle operates the turning on and off of the motor. This, thereby

increases and decreases the speed of the motor. The switching characteristics are performed

with the help of a potentiometer whose resistance value is changed. With increase in

resistance, the speed decreases and with decrease in resistance, the speed increases.

Space vector modulation is a mathematical procedure which is applied for control of the

pulse width modulation. It is opted for the generation of alternating current waveform to

run the motors at variable speeds. There are changes of Space Vector Modulation that

affects the computational requirements. This acts as an inverter circuit. The output from

this is provided to a BLDC motor since a DC motor will not run on an inverter output.

The PWM technique is a preferred speed control techniques for a DC motor. A high

frequency chopper signal with specific duty cycle is increased by switch signals. When the

power supply is on, the DC motor speed starts increasing if we turn off the power supply

before it acquires the rated speed, its speed decreases. In fast succession of switch on and

switch off steps, the motor speed is modulated. For this we use PWM modified to SVPWM

which runs the motor.

2

1.2 METHODOLOGY

Pulse width modulation (PWM) is a method of deceasing the average power

delivered by an electrical signal by cutting it into discrete parts. The average value

of voltage fed to the load is controlled by turning the switch between supply and load on

and off at a fast rate. The longer the switch is on compared to the off periods, the higher the

total power supplied to the load. Pulse width modulation uses a rectangular pulse wave

whose pulse width is modulated which causes variation of the average value of the

waveform. If we consider a pulse waveform, with period, low value, high value, and a duty

cycle.

In this project, the PWM circuit is used and improvised according to our own needs

for higher voltage. Along with these the basic concept of skateboard parts are studied and

manipulated to our needs so as to attach a motor to it. The skateboard is fabricated by

keeping in mind the roads of India so that it can run on rough terrain, not only on well-

developed roads. This problem is solved by providing a ground clearance is provided which

meets our requirement. Similarly conventional skateboard wheels are not used so as to

modify the initial project.

1.3 BLOCK DIAGRAM

The mode of operation implemented in this scenario is altering of the duty cycle

width with the change in the voltage supply. This is done by changing the potentiometer

settings to achieve the desired voltage which gives the desired speed. Pulse Width

Fig.1.1 Block diagram showing control flow of dc motor

Modulation can be the figure 1.1 shows the general block representation of the

3

Implementation of DC Motor Driven Electric Skateboard Using Space Vector Pulse Width

Modulation (SVPWM).

1.4 EXPLANATION OF BLOCK DIAGRAM

A battery source is connected to the switching circuit-Pulse Width Modulation. The

switching pulse is provided from this electronic circuit to the DC motor which will be

mounted on the skateboard.

The SVPWM is an electronic circuit which generates pulses in response to the input

from the throttle. The change in the width of the pulses, which is the change in duty ratio

of the circuit, leads to a change in the speed of the DC motor.

The change in level of voltage is decided by a user or rider. The throttle present here

is a potentiometer whose value can be altered. The voltage applied is proportional to the

motor speed. The DC motor is finally then interfaced with the chain and wheel assembly

through a sprocket chain system. This helps in rotation of the wheels and assists in the

movement of the skateboard.

1.5 LITERATURE SURVEY

The following papers were studied in depth for a better understanding of the concept

at hand. The literature survey was conducted across various journals to verify the theory

under various circumstances to create a further cost efficient technique.

[1] EFFECT OF PULSE WIDTH MODULATION ON DC MOTOR SPEED:

Cosmas Tatenda Katsambe, Vinukumar Luckose, Nurul Shahrizan Shahabuddin

Giapjournals, June 18, 2017

It is seen, in the paper that more is the ON period of the duty cycle, the higher voltage

is applied across the motor terminals. This leads to the stronger the magnetic flux inside the

armature windings. Therefore, the motor will rotate faster. The microcontroller gives an

ease of control for controlling the speed by changing the duty cycle of the PWM pulse. The

changes of the PWM on the motor voltage and speed has been presented here. Pulse width

4

modulation can implemented yields pulses with changing width. The instant rise and fall

of the PWM signal decreases the time for the switching transition and the power loss caused

due to it. This paper shows a DC motor speed controller system using the pulse width

modulation methodology. The PWM circuit present is used to change the width of the duty

cycle and hence change the speed of the motor by altering the motor voltage supply. The

motor voltage and revolutions per minutes is observed at different duty cycle rates. The

paper shows that when the duty cycle is increased, a higher amount of voltage is applied to

the motor. This, in turn, causes stronger magnetic flux within the windings of the armature.

And also increases the RPM. The features, behaviour, and performance of the DC motor

speed control system was studied. In this paper, a PIC microcontroller and a buck converter

are used to control the DC motor speed.

[2] DC MOTOR SPEED CONTROL USING PWM :

K. Priyanka, A. Mariyammal

International Journal of Innovative Science and Research Technology, March 13, 2018

The speed control of the motor is controlled by the PWM and it is

• Low cost.

• It is reliable one.

• It is efficient and long lasting.

• The speed will be in constant at different loads.

• It is more comfortable to use in industries for speed control of the motors.

Dc motors are usually used in industries so the authors implied PWM method to modify

the DC motor as per the requirements. An AT89S52 micro controller is utilized to provide

the pulse width modulations. L293D IC is drives the motor which consists of 2 H-Bridge.

A 555 timer is present with an opto-coupler to detect the speed of DC motor. A rectifier

circuit is used for supplying power to the setup. This paper puts forth a simple way to control

the speed without the use of any complex or costly materials.

[3] PWM BASED SPEED CONTROL FOR A DC MOTOR:

Pratik J Patel, Hardeep, J Patel, Apeksha D Unadkat, Chintan U Patel,

International Journal of Science, Engineering, and Technology Research, April 4, 2017

5

In this paper, we observe how the authors use a microcontroller based method to

control the speed of a DC motor. The microcontrollers use PWM technique for this.

This project is also cheaper than conventional methods, not complex, saves energy, and is

pragmatic in nature. Here, PWM is used to alter the duty cycle which in turn manipulates

the speed of motor. This Project focuses on controlling the speed of a DC motor with the

help of a PWM circuit and the 8051 arrangement microcontroller. The frequency of rotation

of the DC motor corresponds to the voltage applied across the terminals of it. If the voltage

is changed, the speed can be similarly, altered. This paper states this stated ideology to vary

the speed of the DC motor by modifying the duty cycle of the pulse connected to it. This

project implements 2 units along with the microcontroller, which is then used to manipulate

the speed of motor. A motor driver IC is in connection with the microcontroller for receiving

modulation signals and sending the result for the control of the motor.

[4] SPEED CONTROL OF BLDC MOTOR USING PWM TECHNIQUE.

Rajesh M Pindoriya, Rajendran. Priyesh Chauhan

International Journal of Advanced Engineering and Research Development, March 2014

For a method to be efficient and reliable is essential for the working of any motor

drive and its further development. Residential and commercial appliances use predictable

motor drive knowledge. A brushless DC motor is known for having better efficiency, lesser

maintenance, and advanced cost. Therefore, the authors try to develop a low-cost but

effective BLDC motor controller. This is where pulse width modulation comes in. PWM

has been various times in electronics circuit. PWM control is the most self-sufficient

procedure that is offered by a simple method for governing of analog arrangement with

digital output. The paper shows that the Pulse Width Modulation depends on the FPGA

speed and duty cycle prerequisite. In this paper, BLDC motor drive controlled using FPGA

controller.

[5] SPEED CONTROL OF DC MOTOR.

Ľubica Miková, Ivan Virgala, Michal Kelemen

Sciepub, 2016

6

The paper compacts with design and regulation for DC motor and research with

special attention to on speed control. First, the mathematical prototype of DC motor was

created. For the speed control, 2 ways are used, which are: frequency shaping method and

pulse modulation control. For simulating the mathematical model of the proposed theory,

the authors used Matlab program with Simulink. Both approaches are simulated and

compared accordingly.

1.6 INFERENCE FROM LITERATURE SURVEY

From the literature survey performed above, it can be said that the motor, whether

DC or BLDC, speed can be manipulated to fit our requirements. The circuit will be

efficient, cheap and will have a large impact over several land based terrain for the means

of communication. This enabled us to pursue this topic in a much larger depth.

1.7 PROPOSED OBJECTIVE

The main objective of this project work is to design an improved method of

transportation. It will provide a cheaper means of transportation. Efficient operation for

lesser cost. Easy maintenance for layman. Protecting the environment from pollution.

Usable on all land-based terrains for operations.

7

CHAPTER 2

PULSE WIDTH MODULATION

2.1 INTRODUCTION TO PULSE WIDTH MODULATION

Pulse width modulation speed management is a result of driving the motor with a

continuous series of “ON-OFF” pulses. By altering the duty cycle, the fraction of the

time during which the output voltage is “ON” to once it is “OFF” changes. During the

alteration of the pulses, the frequency is kept constant.

This value of ON and OFF time can be manipulated as per the requirements. PWM is

done by using electronic switches (transistors) which gives the following advantages:

• The power loss in the transistor is very low because the switching sequence in

transistor means it is either fully “ON” or fully “OFF”. The transistor does not

have an intermediate state.

• Voltage amplitude of the motor is maintained at a constant level so that the motor

will always be at full strength. The result is that the motor is moving much slower

without stalling.

The 555 timer is an IC which is used for timers, pulse generation, and oscillations.

They are used to assist with time delays, as an oscillator, and even as a flip-flop element.

Fig.2.1 Change in pulse width causes change in average voltage level

8

When the duty cycle is reduced, the pulse width is narrower. This leads to the

average voltage level being less. This can be seen visually in figure 2.1. in the same way,

the wider pulse width leads to an increase in voltage levels and hence, a higher average

voltage.

The simplest way to generate a PWM signal is the intersective method, which

requires only a sawtooth or a triangle waveform and a comparator. When the value of the

reference signal is more than the modulation waveform, the PWM signal (magenta) is in

the high state, otherwise it is in the low state.

2.2 TYPES OF PULSE WIDTH MODULATION

The types of PWM techniques are: 1) Single Pulse Modulation 2) Multiple Pulse

Modulation 3) Selected harmonic elimination PWM 4) Minimum ripple current PWM 5)

Sinusoidal-pulse PWM 6) Space Vector PWM

Among all of these, SVPWM is considered a better technique of PWM

implementation, as it provides the following advantages, (i) Better fundamental output

voltage. (ii) Useful in improving harmonic performance and reducing THD (iii) Extreme

simplicity and it is easy and direct hardware implementation in a Digital Signal Processor

(DSP). (iv) SVPWM can be efficiently executed in a few microseconds, achieving similar

results compared with other PWM methods.

2.3 SPACE VECTOR PULSE WIDTH MODULATION

Space vector PWM is an algorithm which is used to control the pulse output of the

circuit. It is used for the production of alternating current to operate the motor at varying

speeds. There are variations of SVM that result due to varying computational requirements.

A three-phase inverter circuit converts the DC supply, with the help of a combination of

switches, to give 3 output lines which is then connected to a motor. The switches are

controlled in a way where at any given time the two switches on the same leg are not turned

on. This would result in a short circuit. This demand can be fulfilled by the complementary

working of the switches on the same leg. This leads to 8 distinct possible switching

operational vectors for the inverter. It includes 6 non-zero switching vectors and 2 zero

9

vectors.

To implement SVPWM, a reference signal is considered whose frequency is

assumed to be fs. This signal is generated from three separate phase references using the

αβγ transformation. The vector is then processed with the help of a combination of the two

neighboring active vectors and one or both of the 0 vectors.

Fig. 2.2 Space vector diagram representing six sectors

The diagram 2.2 represents the phasor diagram of the vector representation of space

vector pulse width modulation. The 6 sectors are represented with a hexagon whose

diagonals depict the 6 vectors. The seventh and zeroth vector is the mid-point which holds

zero magnitude. The table 2.1 shows the switching combination for the modulation.

Table.2.1 Vector tab le for switch combination and voltage output

10

2.4 SVPWM VS PWM

The SVPWM is considered an improved technique of PWM implementation as it

has some advantages over SPWM in terms of better implementation of dc-bus voltage,

reduced switching frequency and low current ripple. SVPWM is better in the following

ways:

• It has a better fundamental output voltage

• Reducing harmonic performance and THD

• Easier hardware implementation in digital signal processor.

SVPWM can be efficiently executed in a few ms, achieving similar results

compared with other PWM methods. One of the earliest modulation signals for carrier-

based PWM is sinusoidal Pulse Width Modulation (SPWM). The SPWM technique is

based on the comparison of a carrier signal and a pure sinusoidal modulation signal. The

SVPWM technique calculates and computes the duty cycles but SPWM technique derives

through comparison. The utility rate of the DC voltage for traditional sinusoidal PWM is

about seventy eight percent of the DC bus voltage, which is far less than that of the six-step

wave. This technique can be used in single-phase and three-phase inverters. The SVPWM

technique can increase the fundamental component by up to 2.7 that of SPWM. The

fundamental voltage can be increased up to a square wave mode where a modulation index

of unity is reached. The SVPWM is significantly better than SPWM by approximately

fifteen percent.

2.5 APPLICATIONS

• Servos: PWM is used to control servomechanisms

• Telecommunications: In telecommunications, PWM is a form of

signal modulation where the widths of the pulses correspond to specific data values

encoded at one end and decoded at the other. Pulses of various lengths will be sent at regular

intervals.

• Power delivery: PWM can be used to control the amount of power delivered to a

load without incurring the losses that would result from linear power delivery by resistive

11

means.

• Voltage regulation: PWM is also used in efficient voltage regulators. By switching

voltage to the load with the appropriate duty cycle, the output will approximate a voltage

at the desired level. The switching noise is usually filtered with an inductor and a capacitor.

• Audio effects and amplification: PWM is sometimes used in sound (music)

synthesis, in particular subtractive synthesis, as it gives a sound effect similar to chorus or

slightly detuned oscillators played together. (In fact, PWM is equivalent to the difference

of two sawtooth waves with one of them inverted.

• Electrical: SPWM signals are used in micro-inverter design. These switching

signals are fed to the FETs that are used in the device.

12

CHAPTER 3

WORKING PRINCIPLE

3.1 CIRCUIT DIAGRAM

Relating to the internal operation of the 555 timers when the voltage of capacitor

C1 goes below 1/3Vcc pin2 is triggered which is attached to the capacitor as well as to a

lower comparator which then gives a high output to the R of SR flipflop. Q of SRFF goes

low so here high op from the pin3 which again starts charging the capacitor C1. During that

time, the motor is in off state since Q1 is not getting any Base current so MOSFET Q1 is

switched off. Between level 1/3 and 2/3 Vcc the previous state is continued, so pin3 is

giving output and C1 keeps charging through D1. As C1 crosses 2/3Vcc, pin6 is triggered

which is connected to C1 and also to upper comparator comparing to 2/3Vcc. Comparator

gives a high signal on S so Q goes high, switching the transistor on so that pin7 sources

current from Vcc which is limited by the 10K resistor and is sent to base of transistor Q1

which then turns on the motor. C is getting discharged through pin3 to ground. As the

voltage across C goes below 1/3Vcc, this cycle starts again. The control of this on and off

period causes change in the waveform’s width. If period of being on is greater than period

of being off the speed increases and vis versa.

Fig.3.1 555 timer internal logic circuit

13

Fig.3.2 Basic 555 timer circuit for PWM

There are two methods to change the on and the off period. One is changing the

capacitance of the capacitor i.e. if we increase the capacitance then it will take more time

to charge the capacitor so the off period will increase and if we decrease the capacitance

the off period will reduce. Second method is to use a resistor in series with the capacitor.

If the resistance is more during charging then it will take more time to charge so

more off time and if it is less during charging then it will take less time to charge so less off

time. Similarly, if the during discharging if resistance is more then on time will be more

and if it is less then lesser on time. Manipulating this method, we can change the on and off

time so in turn changing the speed accordingly.

In the circuit, we have used a potentiometer to apply the second method. So during

charging the current is through D1 and during discharge it’s from D2. Turning the

potentiometer, we can change the resistance during charging and discharging therefor

controlling the speed. Additional two more components are used which are 12v Zener diode

and 270ohm resistor. 12v Zener diode is to protect the IC from high voltage.

14

3.2 MODIFIED CIRCUIT DIAGRAM

The initial circuit development faced several heat related problems. The MOSFET

burn out was the first and foremost concern. This problem had to be solved before the circuit

could cause serious damage to the developer or the user. Precautions against extreme heat

and fire was the first priority during the developing phase.

Fig.3.3 Modified 55 timer PWM circuit

To solve the heat issue and to avoid the burning up of the MOSFET, current limiters

were used for the purpose as shown in figure 3.3. Ten current limiters of 10ohm each have

been placed in parallel. This helps to reduce the sudden current spike when we start the

motor. With the increase in resistance, and decrease in the starting current, the losses

decrease tremendously. This in turn prevents the fire hazard as faced earlier. Voltage

regulators can also be modified into the circuit to step down the circuit voltage from the

battery to provide gate pulse for the FET.

15

CHAPTER 4

MATHEMATICAL MODELLING

4.1 FRICTION CALCULATION

The main objective is to provide enough force to overcome weight of the vehicle

and the driver. This has to be calculated by taking the respective weights. The weight of

skateboard with the motor mount is estimated to be 20kg. Therefore, considering a 60kg

person the total weigh will be 80kg.

The required force depends on the frictional coefficient which are of two types

dynamic frictional coefficient and static frictional coefficient. But to move a stationary

vehicle we only need that force which can make the vehicle start to move hence we only

need static frictional coefficient.

Now, taking μ as the static friction coefficient and g as the gravitational acceleration

due to earth.

Force = Mass x Acceleration due to gravity x Static frictional coefficient

F= m*g* μ

=80*9.8*0.6

=470.4N

Now we need the force for each wheel which is

F/4=118(approx.)

So, torque will be

Torque = force x radius of wheel in meter

T=118*(radius of wheel in meter) =118*0.1016=12Nm

From this we can conclude that we need more than 12Nm torque to move the object.

This brings us to the gear ratio that is the ratio of the angular speed of the initial or driving

member of a gear train or equivalent mechanism to that of the final or driven member.

In simpler terms it is the no of times a driven gear rotates for one revolution of the driver

gear. Also gear ratio will determine how much torque will be given out from a particular

16

motor.

So, taking care of the radius of the wheel we will take a sprocket with radius less

then, the wheel radius, therefore assuming a 33T sprocket having radius 0.066m. Having

11T on motor.

So, the gear ratio will be:

GR (gear ratio) =33T/11T=3

4.2 CURRENT LIMITER CALCULATION

Inrush current is the instantaneous high input current drawn by a power supply or

electrical equipment at turn-on. This arises due to the high initial currents required to charge

the capacitors and inductors or transformers. In this case the inrush current arises due to the

winding of the DC motor. The inrush current can rise up to three times the nominal current

and can considerably damage the circuit. The solution for this is inrush current limiters

which suppress this inrush current.

Step1: Calculate inrush current

(a)Know your watts

Power in watts of motor is = 250W

(b) Calculate steady state current

SSC= 250watt/24v

=10.4166A

(c) Calculate inrush current

Inrush current= three times steady state current=3*SSC=31.25A

Step2: Calculation to determine the energy an Inrush Current Limiter must absorb without failure

E= input voltage * inrush current * duration if inrush

=24v * 31.25A * 0.2sec

=150joules

17

Step3: Calculate to determine minimum zero power resistance

Goal is to reduce inrush current to 50%

So max desired inrush current is 15.625A

Rmin = input voltage /max desired current

=24v /15.625A

=1.536ohm

4.3. TRUCKS

Channel trucks design is used which are common on mountain boards, and are made

up of an axle mounted to the truck bottom piece.

They are mounted to the deck using nuts and bolts, on an angle, (usually 35°).

When the board is tilted laterally the axles turn together to angle the wheels in the direction

of the turn.

Springs are mounted between the hanger and the axle housing on each truck to

provide resistance to the lean of the rider during turning. Springs are there to return the

deck to center after a turn has been performed.

Fig. 4.1 Trucks working

18

CHAPTER 5

SOFTWARE SIMULATION

5.1 ELECTRONICS

The electronics simulation for this project has been studied and performed as

follows. The simulation has been performed across various platforms to achieve the desired

output. The simulation of pulse width modulation circuit, with the help of a 555-timer was

simulated. The Space Vector Pulse Width Modulation was performed to increase efficiency

in AC based circuits.

Fig.5.1 Simulation diagram

In the above figure 5.1, it can be inferred that the 555 timer pulse width modulation

circuit provides a variable voltage level which can be altered with the help of a variable

resistance present in the form of a potentiometer.

19

Fig.5.2 Schematic diagram

In the above figure 5.2, to solve the heat issue, current limiters were used. Ten

current limiters of 10ohm each have been placed in parallel. This helps to reduce the sudden

current spike when we start the motor. With the increase in resistance, and decrease in the

starting current, the losses decrease tremendously. This in turn prevents the fire hazard as

faced earlier. Voltage regulators can also be modified into the circuit to step down the

circuit voltage from the battery to provide gate pulse for the FET.

Fig.5.3 MATLAB simulation diagram

Figure 5.3 displays the MATLAB Simulink model of the space vector pulse width

modulation. Three pulse input is provided to the circuit. The inverter circuit does its work

and the output is fed to the display. The modulated wave is used for this project work.

20

5.2 MECHANICAL

Before starting the fabrication of all the mechanical parts an overall 3D model was

made in SOLID WORKS cad software. This gives a basic idea how the finished project

will look.

The parts designed on SOLID WORKS were made close to realistic measurements.

Fig.5.4 Motor mount back view

The Fig.5.4 and Fig.5.5 are the back and front view of the motor mount where motor

is stably placed by giving sufficient support. Motor mount is a square hollow metal rod

which is welded on the trucks rod. The motor is placed on this rod via a metal plate such

that this plate can be adjusted to provide sufficient tension on the sprocket chain.

Four slits of metal plate are welded on the motor base plate and holes are drilled on them.

This allows the base plate to slide on the mount rod and screws can be used to fasten the

base plate to the mount rod with sufficient tension so the arrangement does not move. The

trucks, as can be seen in the figure gives better balance to the rider.

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Fig.5.5 Motor mount front view

In the figure 5.5, we can see the screw and bolt placement on the wheel assembly.

It provides a diagonal view to the motor mount and trucks arrangement.

Fig.5.6 Skateboard

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Fig.5.6 shows the basic skate board design without the motor mount. It also shows

the function of the trucks to provide direction while standing on the skate board.

When the Deck is tilted on one side the trucks make the wheels to rotate at the same

direction causing the Skate board to turn towards the intended direction of the rider.

This is similar to the steering system in cars where the board is the steering wheel in the

car.

Fig.5.7 Skateboard with motor mount

The above Fig.5.7 depicts the diagonal view of the entire skateboard simulation.

The wooden board sits on a pair of truck system which has springs to control its movement.

The truck system in turn sits on two parallel rods which are connected to the four wheels.

Motor mount is visible with the motor on top of it. The entire model is simulated according

to real life measurements.

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The next simulation to be done was the sprocket. A sprocket is a key element to run

a chain and wheel system. It helps in transferring the energy from the motor to the wheel.

Fig.5.8 Sprocket isometric view

Fig.5.9 Sprocket top view

Fig 5.8 and Fig 5.9 show the 3D model of motor sprocket which is the driver

sprocket. The sprocket was first simulated in AutoCAD with the required measurements to

create one fitting to the said project. It was then 3D printed for confirmation. The CNC

machine was employed for the manufacturing process of this sprocket. A key system was

designed to ensure proper working of it based on the need. The sprocket designed is fit in

with a gear and chain system onto the wheel. The motor rotates and pulls the chain which

in turn results in the movement of the skateboard.

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CHAPTER 6

HARDWARE

After the simulations were performed, the practical hardware implementation was

performed. The manufacturing and development phase initiated.

Fig.6.1 Bread board

The above diagram 6.1 shows the breadboard made for the phase one testing of the

skateboard electronic circuit. The potentiometer visible in the front is present as a variable

resistance which changes the average voltage level. Jumper wires act as conducting wires.

This was the electronics circuit used to run a low rating motor to verify the methodology

of pulse width modulation.

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Fig.6.2 Trucks component

Fig.6.3 Trucks component

Fig.6.2 and Fig.6.3 show the main components of the truck system. The Fig.6.2

provides an angle of 45degree which acts as a pivot allowing the change of direction.

Fig.6.3 consists of two brackets which are free to move in concentric rotational way. One

bracket is connected to the pivot component and other is connected to the axel rod for the

wheels. A spring is attached to this setup so that the trucks return to their original position

after the turn.

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Fig.6.4 Board

The skate deck is the flat board that you stand on when skateboarding. A shortboard,

is ideal for street skateboarding. A wooden plywood in figure 6.4 shows the skateboard

deck for our project. The board is thick enough so that it does not break down. It has to be

durable, should not get ruined by water, and should not need constant maintenance.

Keeping these points in mind, a suitable material was chosen for the skateboard. The

wooden piece was cut up as per the measurements and holes were drilled on either end for

the truck system to be fixed just below it.

The skateboard deck can be modified to have a better look. It can be updated as per

the rider. The deck should also be able to withstand the stress at different forces when the

road on which the rider is using is not a well-constructed road.

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Fig.6.5 Wheel assembly front view

Fig.6.5 and Fig.6.6 shows the wheel assembly. The wheel assembly used for

providing the torque generated by the motor to wheels in order to make the skateboard

move forward.

Fig 6.6 Wheel assembly back view

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The wheel assembly consists of a sprocket attached to one of the wheels firmly with

the help of wooden blocks cut in the shape of the void in the wheel and a hole is drilled

through the wooden blocks. These wooden blocks help to make a immovable joint with the

screws which are welded on the sprocket. When the motor sprocket rotates the chain drives

the sprocket attached to the wheel and the whole wheel assembly rotates. This in turn

pushed the whole skateboard forward.

Fig.6.7 Trucks and wheel assembly

The figure 6.7 shows the wheel and truck attached. A metal rod is present whose

either end has a wheel and bearings attached. One of the bracket of the trucks is screwed in

the rod. This makes it the bottom most part of the skateboard. This arrangement is present

at both, front and back end, of the skateboard. However, the arrangement present in the

back end has a wheel which is chained to the motor and sprocket. This will enable it to

rotate and in sync with it, all the wheel rotate. The skateboard will hence move.

Fig.6.8 CNC machine constructing sprocket

Fig.6.8 shows the fabrication the Motor Driver Sprocket in CNC machine which was

previously 3D printed.

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Fig.6.9 Motor mount and wheel assembly

The figure above shows the motor mount assembly. The motor is welded to

the sprocket. This is connected to the chain system which rotates the wheel.

Fig.6.10 Skateboard with mechanical parts isometric view

Figure 6.10 show the final skateboard in an isometric view.

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Fig.6.11 Electric Skateboard side view

31

CHAPTER 7

RESULT AND DISCUSSION

7.1 RESULT OF SIMULATION

The results of all the simulation performed across various software gave us positive

results. These results are discussed below along with appropriate pictures. The results

obtained were extremely useful in defining the real time scenarios and the variable factors.

Fig.7.1 Potentiometer at 15%

Figure 7.1 shows the output of the duty cycle when the potentiometer is kept at 15%

from the initial off state. The on time is much greater, as can be seen, compared to the off

time. This gives us a higher average voltage in result. This in turn will result in the motor

working at a higher speed. As the potentiometer is further increased, we can achieve the

following two states. Figure 8.2 shows a 50% operation. The on and off times are equal and

the average motor speed is reduced. In the figure 8.3, the average speed is very low. Here,

the potentiometer is at 75%. The potentiometer can stop the skateboard if made to a 100%.

Output- Potentiometer at 15%

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Fig. 7.4 MATLAB output

Figure 7.4 gives the output of the MATLAB simulation of space vector pulse width

modulation. The 3 output AC waves are 120 degrees apart. They have decreased harmonics.

The output wave proves that the space vector pulse width modulation method is more

efficient that the normal pulse width modulation in terms of losses and power usage.

Fig.7.5 Speed controller PCB

Figure 7.5 displays the PCB which was printed for the above modulation circuits to

be used in the skateboard.

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7.2 RESULT DISCUSSION

The electric skateboard was successfully implemented with the discussed

technology. The pulse width modulation circuit in connection to a DC motor runs the

skateboard at any desired speed within the range. It implements a 555 timer for the circuit.

The potentiometer helps in the variation of the pulse width which manipulates the output

voltage of the motor. This helps in the speed control of the skateboard.

This project helps in reduction of pollution. Development of a circuit suitable for the

application was done. The skateboard made was cheaper than the present mountain boards.

Clearance is provided keeping in mind Indian terrains so that it can be used on any land

based terrains. The setup requires very less maintenance.

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CHAPTER 8

CONCLUSION

8.1 CONCLUSION

The speed of the BLDC motor is being controlled by SVPWM circuit with a 555

timer. The simulation model of the skateboard was designed and studied. The speed of the

motor is successfully controlled by a potentiometer which changes the duty ratio of the

circuit.

The given circuit proves to be efficient as SVPWM results in very low loss of power

due to the use of transistors and less voltage drop across itself. The motor voltage at different

duty cycle periods is obtained. This is because with the increase in duty cycle, additional

voltage is applied to the motor. This means it will lead to a stronger magnetic flux within

the coil windings.

Therefore, it increases the revolutions per minute. The individualities and

performance of the BLDC motor speed structure was studied. The skateboard is constructed

out of wood and the metal parts is used for developing the truck system. The trucks regulate

the turning of the board. The wheels chosen are in accordance with the Indian roads and

will be able to operate on off-roads and is highly cost efficient as compared to mountain

boards.

8.2 FUTURE WORK

The future work on this project can be modified as follows:

(i) Parallel MOSFET combination circuit

(ii) Buck converter for higher efficiency

(iii) Better, sleeker design for efficiency

(iv) Better heat dissipation design

36

REFERENCES

[1] Effect of pulse width modulation on dc motor speed. Cosmas Tatenda Katsambe ,

Vinukumar Luckose, Nurul Shahrizan Shahabuddin

[2] DC Motor Speed Control Using PWM 306.68 KB. Priyanka , A. Mariyammal

[3] PWM Based Speed Control for a DC Motor. PJ Patel, HJ Patel, AD Unadkat, CU Patel,

AP Sanjay

[4] Speed Control of BLDC Motor using PWM Technique. Rajesh M Pindoriya, Indian

Institute of Technology Mandi, S Rajendran. Priyesh Chauhan. National University of

Singapore

[5] Speed Control of DC Motor. Ľubica Miková, Ivan Virgala, Michal Kelemen

[6] Speed Control of DC Motor by using PWM” Khan Masoom Raza1, Mohd. Kamil1,

Pushpendra Kumar1 Electrical Engg Department, MIT Moradabad

[7] PWM Speed Control DC Motor Drive Power Design Zhenyi Xu, Yu Kang

[8] https://www.electronics-tutorials.ws/blog/pulse-width-modulation.html

[9] https://electronicsforu.com/resources/learn-electronics/555-timer-working- specifications

[10] https://learn.sparkfun.com/tutorials/pulse-width-modulation

[11] https://www.techopedia.com/definition/9034/pulse-width-modulation-pwm

[12] Bhimbra, P.S., Power Electronics Principles, Second Edition McGraw-Hill, 1992.

[13] Wikipedia

[14] Bakibillah,A.S.M.,Rahman, N., & Zaman, U. A. (2014).Microcontroller based Closed

Loop Speed Control of DC Motor using PWM Technique. International Journal of

Computer Applications.

[15] Gupta, R., Lamba, & padhee, (2012). Thyristor based speed control techniques of DC

motor: A comparative analysis. International Journal of Scientific and Research

Publications

[16] Kapil, P.N., &Patel, K. (2015).Simulation of PWM controller based DC motor.

International journal of current engineering and scientific research.

[17] PWM based speed control for a DC motor. Pratik J Patel, Hardeep J Patel, Apeksha D

Unadkat, Chintan U Patel, Asst. Prof. Sanjay Bhanderi.

[18] Speed control of DC motor by using PWM” Khan Masoom Raza1, Mohd. Kamil,

Pushpendra Kumar , Electrical Engg Department, MIT Moradabad

[19] DC motor speed control using PWM. K. Priyanka, A. Mariyammal; Department of

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Electrical and Communication Engineering, Vivekanandha College of Engineering for

Women (autonomous), Tiruchengode.

[20] Speed control of dc motor using pwm: Amit Kumar Yadav, Annu Kumari Chaubey Asst.

Prof., Department of Electrical and Electronics Engineering, UG, Department of Electrical

and Electronics Engineering, Raj Kumar Goel, Institute of Technology for Women, UP

[21] Effect of pulse width modulation on DC motor speed Cosmas Tatenda Katsambe,

Vinukumar Luckose, Nurul Shahrizan Shahabuddin; Department of Electrical Engineering,

Faculty of Engineering, Nilai university.

implementation of dc motor driven electric …

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