Automatic gear transmission in two wheelers using embedded system

INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
– 6480(Print), ISSN ENGINEERING AND 3, Number 2, July-December (2012), © IAEME
0976 – 6499(Online) Volume TECHNOLOGY (IJARET)

ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 3, Issue 2, July-December (2012), pp. 164-175
IJARET
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2012): 2.7078 (Calculated by GISI)
©IAEME
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AUTOMATIC GEAR TRANSMISSION IN TWO WHEELERS
USING EMBEDDED SYSTEM

P. Alexander M.E.1, T. Sudha M.E.2, M. Omamageswari M.E.3
1
(Department of Instrumentation & Control Engineering, Sri Manakula Vinayagar Engineering
College, Puducherry, India, aim4high@gmail.com)
2
College, Puducherry, India, t.sudhavelu@gmail.com)
3
College, Puducherry, India, omamagi@yahoo.com)

ABSTRACT
In this study, a gear shifting mechanism was designed and applied on an auto clutch featured
bike to make the gear transmission process faster and less destructible for the diver using
Embedded System design. The present automatic transmission is fully mechanically controlled
and costs very high and it is not suitable for small displacement engines. But the gear
transmission mechanism designed makes driving easier and to achieve efficient driving. This
new device must be reliable, has small dimensions, economical and low maintenance cost. This
project aims to improve the gear shifting process with a suitable control mechanism to
implement in clutch featured bikes. According to the suggested gear shifting method, the
microcontroller selects the transmission gear as per the speed of the vehicle without any human
interference. The head light control is designed which dims and dips if any vehicles comes
opposite with high beam. This is a safety feature installed to avoid accidents caused due to high
beam lights having blinding effect on drivers coming from the opposite direction.

Keywords: Automatic gear transmission, automatic headlight control, Digital speedometer,
Inductive proximity sensor, Microcontroller AT89s51.

1. INTRODUCTION
1.1 Overview
The topic of current interest in the area of controller development for automatic
transmissions with a finite number of gearshifts which transmits the gears automatically with
respect to speed. Gearshifts in automatic transmissions involve a change in the power flow path
through the transmission. Advantages of these automatic transmissions include simplicity of

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– 6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 2, July-December (2012), © IAEME

mechanical design and savings in transmission weight and size, which are beneficial in terms of
fuel economy and production costs. This enables gain in fuel economy while meeting drivability
and performance goals, these savings become more significant.
The designed automatic transmission is done in an auto-clutch featured bike which can be
applied effectively and efficiently in a clutch featured bikes with suitable control techniques. The
ultimate goal of our project is to transmit the gears without the human interference and to attain
efficient, safe and easy driving in cost effective way. Microcontroller is the heart of the system
which handles all the sub devices connected across it. We have used Atmel 89s52
microcontroller.
1.2 Automation
Automation is the use of control system to control a process replacing the human
operators. It is a step beyond mechanization, where human operators are provided with the
physical requirements of work.
Automation is now often applied primarily to reduce the human effort thereby to attain
desired operation. Another major shift in automation is the increased emphasis on flexibility and
convertibility in different process.
One safety issue with automation is that it is often viewed as a way to minimize human
error in the system, increasing the degree and the levels of automation also increase the sequence
of error that accidently created in automated systems. Different types of automation tools that
exist in today’s environment are Programmable logic controller, Microcontroller, SCADA, etc.

1.3 Types of Transmission
Manual transmission
Automatic transmission
1.3.1 Manual Transmission
A manual transmission or sequential type is a type of transmission used on motorcycles
and cars, where gears are selected in order, and direct access to specific gears is not possible.
With traditional manual transmissions, the driver can move from gear to gear, by moving
the shifter to the appropriate position. A clutch must be disengaged before the new gear is
selected, to disengage the running engine from the transmission, thus stopping all torque transfer.
1.3.2 Automatic Transmission
An automatic transmission is one type of motor vehicle transmission that can
automatically change gear ratios as the vehicle moves, freeing the driver from having to shift
gears manually and to achieve efficient driving.
1.3.3 Advantages of Automatic Transmission
• Easier to drive in stop-and-go traffic and available in most cars, an automatic
transmission has definite benefits
• The main benefit of automatic transmissions is that they are simply easier to use.
• Fuel efficient.
1.4 Embedded System
All embedded system uses either a microprocessor (or) microcontroller. The software for
the embedded system is called firmware. The firmware will be written in assembly language (or)
using higher level languages life ‘C’ (or) ‘Embedded C’. The software will be simulated using
micro code simulation for the target processor. Since they are supposed to perform only specific
tasks, the programs are stored in ROM.

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An embedded system is some combination of computer hardware and software, either
fixed in capability or programmable, that is specifically designed for a particular function.
Industrial machines, automobiles, medical equipment, cameras, household appliances, airplanes,
vending machines and toys (as well as the more obvious cellular phone and PDA) are among the
myriad possible hosts of an embedded system. Embedded systems that are programmable are
provided with programming interfaces, and embedded system programming is a specialized
occupation.
An Embedded system is a special-purpose computer system, which is completely
encapsulated by the device controls. It has specific requirements and performs pre-defined tasks,
unlike a general purpose personal computer.
Avoids lots of Electronic components.
Build in with rich features.
Probability of failure is reduced.
Easy interface.
1.5 Block Diagram Description
The presented project is aimed to perform operations such as automatic gear
transmission, automatic headlight control, and digital speedometer. Here the speed is the inputs
to the microcontroller unit.
The inductive speed sensor senses the speed of the vehicle from the front wheel and
sends train of pulses as output to the microcontroller unit. The microcontroller unit checks the
pulses for sample time period and calculates the speed of the vehicle.
As programmed, the microcontroller actuates the Relay 1 and Relay 2 through the driver
unit depending on the speed of the vehicle. The DC motor function is to transmit the gear lever
by pole reversal technique which is performed using the relays.
Since it requires slowing down the engine at the time of gear transmission, the supply to
the ignition coil is grounded so as to slow the engine.

Fig.1: Block Diagram of Automatic gear transmission in Two Wheelers
Using Embedded System

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2. HARDWARE DESCRIPTION
2.1 Inductive Speed Sensor
Inductive proximity sensors are designed to operate by generating an electromagnetic
field and detecting the eddy current losses when a ferrous metal target enters the field. The
sensor consists of a ferrite core, an oscillator, a trigger-signal level detector and an output circuit.
The oscillator creates a high frequency field radiating from the coil in front of the sensor
centered on the axis of the coil. When a metal object enters the high-frequency field, eddy
currents are induced on the surface of the target. As a metal object advances into the field, eddy
currents are induced in the target. This results in a loss of energy in the oscillator circuit and
consequently smaller amplitude of oscillation.

Fig. 2: Inductive proximity pickup
The detector circuit recognizes a specific change in amplitude and generates a signal
which will turn the solid state-output “ON” or “OFF”. When the metal object leaves the sensing
area, the oscillator regenerates allowing the sensor to return to its normal state.
The inductive speed sensor has a built-in hysteresis to avoid unwanted switching of the
sensor due to,
• Mechanical vibration of the sensor or the gear wheel
• Electrical interference
• Circuit oscillation at very low rotational speed

Fig.3: Sensor mounting
A larger hysteresis provides a better immunity to disturbances but, on the other hand,
reduces the maximum sensing distance d, as the sensor signal must exceed the hysteresis levels
to be recognized.
2.2 Microcontroller
Microcontrollers are microprocessors with peripheral devices and memory embedded in a
single chip. They are used in almost all modern day appliances controllers and so it is produced
in millions. The most popular microcontroller architecture is Atmel 89s52. There are many

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number of IC manufacturers offering microcontrollers based on this architecture. Atmel is one of
them. The microcontroller 89s52 from Atmel is chosen for this project.
2.2.1 AT89S52
The AT89s52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K
bytes of Flash programmable and erasable read only memory (PEROM). The device is
manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with
the industry standard 80C51 and 80C52 instruction set and pin out. The on-chip Flash allows the
program memory to be reprogrammed in-system or by a conventional nonvolatile memory
programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel
AT89s52 is a powerful microcomputer which provides a highly-flexible and cost-effective
solution to many embedded control applications.
Features
• 8K Bytes of In-System Reprogrammable Flash Memory
• 256 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Three 16-bit Timer/Counters
• Eight Interrupt Sources
• Programmable Serial Channel
• Low-power Idle and Power-down Modes

2.2.2 Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that
can be configured for use as an on-chip oscillator, as shown in Fig.4. Either a quartz crystal or
ceramic resonator may be used. To drive the device from an external clock source, XTAL2
should be left unconnected while XTAL1 is driven, as shown in the figure. There are no
requirements on the duty cycle of the external clock signal, since the input to the internal
clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high
and low time specifications must be observed.

Fig.4: Oscillator connection

2.3 Liquid Crystal Display (LCD)
A liquid crystal display (LCD) is a flat panel display, electronic visual display, or video
display that uses the light modulating properties of liquid crystals (LCs). LCDs do not emit light
directly. The LCD display used in this project is 16*2 type LCD display it consists of 14 pins.

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2.4 Relay Driver Unit
Relays are devices which allow low power circuits to switch a relatively high current and
voltage ON/OFF. For a relay to operate a suitable pull-in and holding current should be passed
through its coil. Generally relay coils are designed to operate from a particular voltage at 5V or
12V.

Fig.5: Relay Driver Unit
The fig.5 shows the basic relay driver circuit. The NPN transistor BC547 is used to
control the relay. The transistor is driven into saturation (turned ON) when logic 1 is written on
the port pin thus turning ON the relay. The relay is turned OFF by writing logic 0 on the port pin.
A diode is connected across the relay coil to protect the transistor damage due to back EMF
generated in the relays inductive coil when the transistor is turned OFF. The LED is used to
indicate that the relay is turned ON or OFF.
2.5 Relays
Relays come in various configurations for their switch contacts, as well as different DC
voltages for to operate their coil. They may be as simple as an on/off switch or as complex as
integrating several switches into one unit. In a "double-pole" configuration, one switch terminal
toggles between two different output terminals. Regardless of the configuration, each switch on a
relay can be "normally open" (NO) or "normally closed" (NC); that is, when the coil is at rest
and not energized, the switch contacts are NO or NC. In an open circuit, no current flows, similar
to a wall light switch in the "Off" position. In a closed circuit, metal switch contacts touch each
other to complete a circuit, and current flows, similar to turning a light switch to the "On"
position.
In the accompanying schematic diagram, points A and B connect to the coil. Points C and
D connect to the switch. Voltage applied across the coil at points A and B creates an
electromagnetic field that attracts a lever in the switch, causing it to make or break contact in the
circuit at points C and D (depending if the design is NO or NC). The switch contacts remain in
this state until the voltage to the coil is removed.
Rated load : 12-28VDC
Coil resistance : <=100m ohms
Coil rated voltage : 3-24VDC

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2.6 DC Motor
The DC motor has two basic parts: the rotating part that is called the armature and the stationary
part that includes coils of wire called the field coils. The stationary part is also called the stator. The
armature is made of coils of wire wrapped around the core, and the core has an extended shaft that rotates
on bearings. The ends of each coil of wire on the armature are terminated at one end of the armature. The
termination points are called the commutator, and this is where the brushes make electrical contact to
bring electrical current from the stationary part to the rotating part of the machine. The stator coils will be
referred to as field coils they are connected in series or parallel with each other to create changes of
torque in the motor.

2.7 Photo Detectors
The MRD500 photodiode used is a p-intrinsic-n (PIN) silicon diode operated in reverse bias. The
very thin p-type conducting layer acts as a window to admit light into the crystal. The reverse bias
voltage maintains a strong electric field throughout the intrinsic region forming an extended depletion
layer. The depletion layer should be thicker than the absorption length for photons in silicon in order to
maximize the efficiency. Any incident photon whose energy exceeds the band-gap energy is absorbed to
produce an electron-hole pair by photoelectric excitation of a valence electron into the conduction band.
The charge carriers are swept out of the crystal by the internal electric field to appear as a photocurrent at
the terminals. The photocurrent is proportional to the rate at which light is entering the diode.
+V

D1
MR500

V signal

R1
10k

Fig.6: Photo Detector Circuit

2.8 Power Supply Unit
Voltage
regulator
7805 Microcontroller
board

To DC
12V 7Ah motor and
Battery
relays

Fig.7: Block diagram of power supply unit

The 7805 is a family of self-contained fixed linear voltage regulator integrated circuits .The 78xx
family is commonly used in electronic circuits requiring a regulated power supply due to their ease-of-use
and low cost. For ICs within the family, the xx is replaced with two digits, indicating the
output voltage (for example, the 7805 has a 5 volt output, while the 7812 produces 12 volts). The 78xx

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lines are positive voltage regulators: they produce a voltage that is positive relative to a common ground.
There is a related line of 79xx devices which are complementary negative voltage regulators. 78xx and
79xx ICs can be used in combination to provide positive and negative supply voltages in the same circuit.
These devices support an input voltage anywhere from a couple of volts over the intended output voltage,
up to a maximum of 35 or 40 volts, and typically provide 1 or 1.5 amperes of current (though smaller or
larger packages may have a lower or higher current rating).
3. HARDWARE IMPLEMENTATION
3.1 Overall Circuit

Fig.9: Overall circuit

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3.2 Pin connection
P2.7 - Inductive proximity sensor
P2.2 - To Relay 1 (upward gear shifting)
P2.3 - To Relay 2 (downward gear shifting)
P2.4 - To Relay 3 (ignition cut off relay)
P3.4 - Enable (LCD command word)
P3.5 - To select data/command register (LCD command word)
P1.0 - D0 (LCD data line)

3.2 DC Motor Connections

Fig.10: DC motor connections
Relay specification:
Relays 1 and 2 – 12V, 25A
Relays 3 and 4 – 12V, 5A
To run the DC motor in both directions to shift the gear up and down pole reversing
technique is adopted. Here relays 1 and 2 are connected to the DC motor and the relays 3 and 4
operate the relays 1 and 2 through the microcontroller respectively. When relay 3 is energized
through the microcontroller units relay 1 is energized and thus the motor runs in anticlockwise
direction and shifts the gear upwards and when the relay 4 is energized opposite action takes
place and shifts the gear downwards.

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3.3 Photo Detector Circuit

MR500 is used as a sensor to detect the light intensity which is silicon photodiode. This
photodiode operates under an oscillator with frequency of 2 KHz correspondingly current is
obtained as output which is proportional to the intensity of the light. A current to voltage
amplifier is used with input current from the photodiode is applied to the inverting terminal of
the amplifier.

Fig.11: Photo detector circuit

The output of the current to voltage amplifier is connected to the relay through the relay
driver unit which operates the functionality of the headlight.

3.4 Project Snapshots

Fig.12: Microcontroller board

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Fig.13: DC motor mounting

Fig. 14: Inductive speed sensor mounting

4. RESULTS ANALYSIS
The Inductive speed sensor output pulses decide the output of the system. The sensor
produces pulses when it crosses the metal target fixed in the wheel. The sets of gear pattern is
decided by the pulses obtained from the sensor and they are tabulated below,

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Table 1: Obtained Output
Sensor pulses Speed (Km/hr) Gear position

1 Less than 5 Gear 1
2 5
Gear 2
3 15
5 20
Gear 3
7 25
9 30
11 35
13 40 Gear 4
15 45
17 50

5. CONCLUSION

The project presented has involved the development and implementation of automatic
transmissions for bikes. The motivation of this work is to implement this idea in clutch featured
bikes with a suitable clutch control. The automatic transmission can be also used in 5 and 6
speed versions by altering few changes in the program. According to the achieved results the
mechanism done is reliable if it is installed in bikes. Using the simplest microcontroller and the
required hardware enables to convert the old traditional semi automatic gear transmission
mechanism to a fully automated one. The application of this mechanism leads to make the
driving process easier and fuel efficient driving can be achieved.

REFERENCES
[1] J-O Hahn1, J-W Hur, G-W Choi, Y M Cho and K I Lee. Department of Mechanical
Engineering, Korea Airforce Academy, South Korea.:”Self-learning approach to automatic
transmission shift control in a commercial construction vehicle during the inertia phase”.
[2] Zhenyu Zhu, Chunxin Xu, College of Mechanical Science and Engineering，Jilin
University, Changchun, Jilin 130025, China.:”Experimental Study on Intelligent Gear-
Shifting Control System of Construction Vehicle Based on Chaotic Neural Network”
[3] Chunsheng Ni, Tongli Lu, Jianwu Zhang, School of Mechanical Engineering, State Key
Laboratory for Mechanical System and Vibration Shanghai Jiao Tong University, 800 Dong
Chuan Road, Shanghai, 200240 China.:”Gearshift control for dry dual-clutch transmissions”
[4] Muntaser Momani, Mohammed Abuzalata, Igried Al-Khawaldeh and Hisham Al-M ujafet,
Department of Mechanical Engineering, Faculty of Engineering Technology, Al-Balqa’
Applied University, Amman, P.O. Box 15008, 11134, Jordan.:” Pneumatic PLC Controlled,
Automotive Gear Shifting Mechanism”

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Automatic gear transmission in two wheelers using embedded system

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