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 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.