30-09-2016, 04:16 PM
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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.
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 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.
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.
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.
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.
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
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.
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.