Remote operated Fork Lift
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Joined: Sep 2010
04-10-2010, 03:19 PM
In general the forklift can be defined as a tool capable of lifting hundreds of kilograms. A forklift is a vehicle similar to a small truck that has two metal forks on the front used to lift cargo. The forklift operator drives the forklift forward until the forks push under the cargo, and can then lift the cargo several feet in the air by operating the forks. The forks, also known as blades or tines, are usually made out of steel and can lift up to a few tons.
Forklifts are either powered by gasoline, propane, or electricity. Electric forklifts relay on batteries to operate. Gasoline or propane forklifts are sometimes stronger or faster than electric forklifts, but they are more difficult to maintain, and fuel can be costly. Electric forklifts are great for warehouse use because they do not give off noxious fumes like gas powered machines do.
Forklifts are most often used in warehouses, but some are meant to be used outdoors. The vast majority of rough terrain forklifts operate on gasoline, but some use diesel or natural gas. Rough terrain forklifts have the highest lifting capacity of all forklifts and heavy duty tires (like those found on trucks), making it possible to drive them on uneven surfaces outdoors.
It is important for forklift operators to follow all safety precautions when using a forklift. Drivers should be careful not to exceed the forklift's weight capacity. Forklift operators also need to be able to handle forklift's rear wheel steering. Driving a forklift is similar to driving a car in reverse, meaning that the driver must constantly steer to keep it moving in a straight line. The driver must be aware of the forklift's ever-changing center of gravity and avoid making any quick sharp turns or going too fast. It is advisable that anyone who operates a forklift be fully trained and licensed.
Forklifts have revolutionized warehouse work. They made it possible for one person to move thousands of pounds at once. Well-maintained and safely operated forklifts make lifting and transporting cargo infinitely easier. This is the general description of a normal forklift truck. To enhances the technology further, this prototype module is constructed with remote technology, there by the operator can walk along with the forklift for better visibility & the container can be placed accurately (precision position). This increases the safety of the operator.
The mechanical structure of this prototype module is constructed with square metal pipes, this structure looks like a rectangular box & the vertical moving mechanism that contains metal forks is assembled over the structure at front side. Since it operates through a remote, it doesn’t contain any steering mechanism. The entire vehicle is designed to drive through four wheels, & four motors are used to drive all the four wheels directly. Two left side motors of front and rear are connected parallel, similarly the other two motors used to drive right side front and rear wheels are also connected parallel. All these four motors are driven through a single ‘H’ bridge DC motor drive package. All the four wheels are directly coupled to the motor shafts independently. The DC Motors are having reduction gear mechanism internally, there by speed is reduced and torque is increased. The detailed description is provided in following chapters.
The fundamental concept involved in the system is to create mechanical movements in the forklift according to the command signals generated and transmitted through the remote designed with RF module. In this concept, the command signal information produced through an activated key interfaced with data transmitting controller, & and accordingly based on the digital code generated by the controller chip, the data is super imposed over the carrier & transmitted as modulated signal. The received signal is demodulated through RF receiver module & the output is fed to another microcontroller unit arranged over the forklift. This controller is programmed to control the motors through H Bridge. This process is called Radio communication, and it is the process of sending information from one place and receiving it in another place without using any connecting wires. It is also called as wireless communication system. In general Radio waves are produced by rapidly changing currents flowing through a conductor. These radio waves spread out in space like ripples produced on the surface of a pond when a stone is dropped in the water. When these fast moving radio waves strike some other conductor placed in their path at a distant point, they produce in the second conductor weak currents of the same nature as the original current which produced these radio waves. Thus a communication link will be established between two distant points. In this project and implimentation work this communication system is playing active roll it is essential to describe the system well, there fore it is described in detail in following chapters.
The forklift mechanism that controls through remote is designed with two different microcontroller chips; both the chips are selected from ATMEL family. The remote controlled card that generates command signals uses 89C2051 IC; this is a 20 pin chip & consumes less energy from the battery, thereby it is selected because this circuit is operated through a small 9V battery pack. The main control circuit accommodated over the forklift is designed with 89C51 chip; this IC is having 40 pins. These are 8- bit controllers widely used for instruments and control applications. The 89C51 is the integration of a microprocessor having 4kb memory, 32 I/O lines, timers, ROM, etc. on a single chip. As this chip is having four ports, two numbers of ‘H’ Bridge packages, manual control keys, RF receiver, etc are interfaced with this single chip. This control circuit is aimed to control the five DC motors according to the command signals received from the transmitter.
Any Micro-controller, that functions according to the program written in it. Here the program is prepared in such a way, so that the system performs the function of a forklift through motors. The program is nothing but an instruction set, & according to the instructions received from the remote, the controller unit carries out the specified task. The instruction set often prepared in binary code, & are referred as machine code, there by this software is called as machine language. Writing a program in such a code is a skilled and very tedious process. It is prone to errors because the program is just a series of 0’s and 1’s and the instructions are not easily comprehended from just looking at the pattern. An alternative is to use an easily comprehended form of shorthand code for the patterns 0’s and 1’s. Micro controller can read and it can store the information received from the remote control unit. Micro-controllers are dedicated to one task and run one specific program. The program is stored in ROM (read-only memory) and generally does not change. If there are any modifications in the function, or errors in the software, the existing program must be erased from the chip & again modified program must be loaded in the chip through chip burner.
Various fields of technologies are included in this project and implimentation work, because this system falls under the subject of Mechatronics. The integration of electronic engineering, mechanical engineering, electrical engineering, & control technology is forming a crucial part in this design. Especially the control circuit designed with microcontroller plays dominant roll in this project and implimentation work. The term mechatronics is used to describe this integrated approach, therefore all above subjects are described in this project and implimentation report in following chapters. Most systems that provide motion and force contain a mixture of Mechanical, Electrical, Electronic, and Digital Components. In fact, today most systems are mixed systems. The design of these mixed systems requires knowledge from all these fields.
To make the project and implimentation work more realistic, much importance is given for practical orientation, therefore a prototype module is constructed for the demonstration purpose. This module simulates the real working system & based on this technology with slight changes in the structure & motor ratings, the system can be converted for real applications. The method of converting rotary to linear motion is implemented in the mechanism. The forklift is designed to move in all directions including reverse direction also.
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